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Character Profiles > Mark Brennan Scott McGregor

Mark Brennan 2010-2011, 2013, 2014
Lives: 24 Ramsay Street
Lived: 26, 30 Ramsay Street
Silbings: Tyler
Occupation: Police Detective, Police Officer, Abseiling Instructor, Mechanic

Erinsborough Police Detective Mark Brennan first encountered the residents of Ramsay Street following the attempt to kill local businessman Paul Robinson by pushing him from the mezzanine at Lassiter's Hotel. As Paul had made numerous enemies in the weeks leading up to the incident, Detective Brennan had his work cut out for him just narrowing down the list of suspects. Prime suspect was Diana Marshall, a business rival of Paul's who he'd crossed once too often. She, however, told Brennan that he should be speaking to Paul's wife, Rebecca, who, only hours before Paul was pushed, had found out, from the woman herself, that Diana and Paul had slept together. Another suspect emerged in the form of Paul's son, Andrew - Paul had threatened to cut him out of his will and Andrew had been heard wishing his father dead. In a misguided attempt to help her ex-boyfriend, Natasha Williams attempted to give Andrew an alibi, but was later forced to admit that she lied, only making things worse for Andrew. Meanwhile, Rebecca's son, Declan, who had been secretly working with Diana to destroy Paul, asked his ex, Paul's niece Kate Ramsay, to lie to the police and give Rebecca an alibi, a request which she reluctantly agreed to.

With the police left with so many leads to follow up, Andrew decided to do some investigating of his own. At first, he suspected that Sonya Mitchell may have had something to do with the crime. Sonya was the girlfriend of Ramsay Streeter Toadie Rebecchi, whose life had been turned upside-down when Paul revealed the truth about Toadie's sham marriage to Steph Scully. After it emerged that Sonya had a criminial conviction for assault in her past, she was taken in for questioning, but soon released to go. Andrew then turned his efforts to Diana and spotted her speaking to a strange man, who then dumped his phone in a bin. Having taken the phone, it later rang and Diana left a message warning the owner to leave town. Andrew gave this evidence to the police, and Diana was again taken in for questioning, but released after a few days as there was insufficient evidence to charge her. At the same time, Paul awoke from his coma and, barely able to speak, implied that Diana had pushed him from the mezzanine. The police headed to her hotel, but she had already been warned and had managed to get away.

Some weeks later, Brennan walked into Harold's Store just as Donna was trying to find a new man for Kate, and ended up caught in the crossfire. Though slightly confused, Brennan followed Kate outside and jokingly warned her not to ride off on her bike with her helmet strap still undone. Later, he caught up with her again, apologising for the helmet strap comment which she didn't take as a joke, and asked her out to dinner. Kate turned him down, but the next day they ran into each other again and she agreed to go for coffee. Kate explained to Brennan how she was a witness to an accident involving Steph Scully running down and killing Ringo on her motorbike, and the lawyers for both sides were hassling her. Brennan listened to her and told her to trust her instincts when giving her evidence, and she then asked him if the offer for dinner was still on. However, when she and Brennan were having dinner, Kate's ex, Declan, took her to one side and reminded her that she'd lied to the police, giving an alibi to Rebecca - who'd actually turned out to be the one who pushed Paul, though only a select few people knew about it. Realising how much trouble she could end up in, Kate took Declan's advice and quickly cut the date short, leaving Brennan confused as she rushed off home to look after her 'sick sister'.

Brennan wasn't about to give up on Kate that easily, though, and they had a coffee together, which was once again derailed by Declan, who insisted that he needed to take Kate out for a driving lesson. Brennan and Declan continued to fight over Kate, but it was Brennan that she was really interested in, and she tracked him down to the gym, boldly walking in on him in the changing rooms, only to get flustered at the sight of him in just a towel. As Kate and Brennan grew closer, Declan continued to try his best to keep them apart, lying to her that Brennan had warned him off. Then, after Lucas accidentally punched him instead of the punching bag, Declan lied that Brennan had hit him. When Kate confronted Brennan about this, he had no idea what she was talking about and decided that the whole thing was just becoming too complicated, so he ended things between them. When Kate found out the truth about Declan's black eye, she went to apologise to Brennan, but he told her that she had a lot of things she needed to sort out before she should think about dating again. But later, Kate went back to the police station and kissed him, in front of his colleagues and made him realise that she was worth the risk.

Meanwhile, the Paul Robinson case rumbled on, with the police no closer to finding the culprit and Paul managing to rule Diana out when he mentioned that he was certain that Diana had left, and hadn't come back, on the evening he was pushed. With Paul and Declan both desperate to keep Rebecca's name out of it, Paul asked Kate to try and find out the status of the case. At dinner that evening, Kate asked Brennan how the case was going and he could only tell her that they were planning to re-interview all of the suspects - and that Diana had now been ruled out. Faking a stomach upset, Kate ended the evening early and told Paul what she'd found out, but the next day, feeling terrible about the whole thing, she warned Paul and Declan that she wouldn't be doing the same thing again, and she wanted nothing more to do with the whole sorry mess. However, when Brennan started talking about interviewing Rebecca again, Paul once again asked Kate to try and find out how much Brennan knew, and whether Rebecca was a serious suspect. When Kate refused, Paul threatened to cut off her trust fund, and she responded by telling him that she wanted nothing more to do with him, removing a locket that he'd given her. Brennan later mentioned that he knew when Kate was being dishonest - such as when she lied about her stomach upset - as she fiddled with the locket and as Kate's behaviour became more and more odd, and she told Brennan that she was certain that Declan hadn't pushed Paul, he reviewed her interview and was shocked to see her fiddling with the locket.

Now certain that Kate had lied to him when giving her alibi for Rebecca, Brennan became a little more wary of her, but bought her a new necklace as a Christmas gift. After a few days of silence, Brennan asked to speak to Kate at the station, showing her the video footage of her interview and pointing out that he suspected she was lying. Kate angrily told him that she also fiddled with the locket when she was nervous and stressed, and the interview had been very stressful for her. Realising that he might have been wrong, Brennan told Kate that he really needed to solve this case to prove himself to his superiors, but he wasn't sure if it was worth sacrificing his relationship with Kate. Things then took an interesting turn when Kate was playing truth or dare at Charlie's, with her friends Donna and Jade and the girls ended up flashing just as Brennan walked in with his boss. He was forced to take the three of them down to the station and give them warnings, but he later caught Kate as she was returning home and told her that he'd made his decision - he was giving up the Robinson case to be with her.

Over the weeks that followed, Brennan grew closer to Kate, and became protective of her and younger sister Sophie when he found out that their housemate Lucas had been doing business with some known criminals at the garage he owned and had started drag racing. As a gambling addict, Lucas was once again struggling to keep on top of things and when he refused to throw the race he was taking part in, he ended up getting beaten up, further grabbing Brennan's attention. When Lucas admitted to Brennan that he'd been involved in illegal races, Brennan and his colleague Megan Phillips went undercover to catch the gang, using Lucas to get in. Wanting to bring down the ringleader of the dodgy car deal and illegal races, Garland Cole, Brennan managed to convince Lucas to wear a wire and arrange another deal, but Kate was growing suspicious and began to wonder if her boyfriend was arranging a surprise birthday present. She followed him to the garage but had to hide when Brennan, Lucas and Garland came back, only for her phone to alert them to her presence. Brennan managed to cover for Kate, but once all of the stolen goods were loaded into the van, Kate blew his cover and he had to arrest Garland, and explain to Kate that he'd been trying to get Lucas out of a tricky situation.

Just as things seemed to be settling down for Kate and Brennan, she found out that Rebecca had left town. Rebecca had given their neighbour Susan a signed statement of no complaint, signed by Paul, which meant that Rebecca could confess in writing but not be charged - however, it would also reveal that Kate had given her a false alibi, so she wanted Susan to persuade Kate to confess first. After thinking things over, and realising how much she stood to lose, Kate finally decided to make a statement, but Brennan was appalled, particularly as he'd given up so much for her, and admitted that he didn't think he could forgive her. After receiving a fine and a good behaviour bond in court, Kate tried her best to move on from Brennan, but then after seeing him in the bar with some work colleagues, she ended up calling him and confessing her love. Realising how stupid she'd been, she and Jade tried to get Brennan's phone from his jacket. After being caught, Kate confessed everything, and Brennan simply deleted her voicemail and walked away.

When Sophie decided to try and reunite Kate and Brennan, and roped in Jade to help, things went slightly wrong when Kate ended up with the impression that Jade and Brennan were interested in each other. A jealous Kate then confronted Brennan, only to end up losing more of his respect, and Jade's friendship, in the process. When Lucas spoke to Brennan, to try and find out if there was any hope at all for Kate, he said that she'd lied to him and he didn't think that he could get past that. Kate accepted this and realised that she needed to move on with her life, but Brennan was less than impressed when she appeared to be moving on with Kyle Canning. Kyle and Kate were already friends, having gone to school together, but after finding work nearby, Kyle started hanging around more and Brennan struggled to contain his jealousy when he saw him with Kate. When Kyle was getting changed in his car one day and accidentally flashed Brennan, the detective used it as an excuse to give Kyle a warning and keep an eye on his behaviour. However, when he then called Kate to the station, just to tell her that Garland Cole had been given 18 months in prison, she and her friends began to realise that he might still be interested, and Lucas encouraged Brennan to do something before Kyle made a move of his own.

Meanwhile, when his flat became infested with insects, Brennan had to find somewhere else to live, and ended up accepting a room at Toadie's place, 30 Ramsay Street, for a few days. The mess and chaos of the house caused problems for neat freak Brennan, but eventually Toadie and Brennan found a way to live together, and Brennan became something of a role model for Toadie's adopted son Callum, who loved hearing about his police work. However, after finally asking Kate out for coffee, Brennan had to cancel when Toadie and Callum asked him to stay home and have nachos with them instead, and the next day, he saw Kate give Kyle a kiss on the cheek and decided to back off once again. Believing that Brennan wasn't interested, Kate went on a date with Kyle, but ended it early and she could only think about her ex. As Brennan's jealousy over Kyle only got worse, Kyle was forced to turn to his rival for help, when he found himself being blackmailed into giving protection money by a corrupt cop, Wes Holland. At first, Brennan couldn't believe that Holland would do something like that, but after seeing some security footage from across the lot, he realised that Kyle was being honest and they set up a meeting, with Brennan arriving and arresting Holland as Kyle handed over the protection money. Though the incident finally ended the feud between Kyle and Brennan, the detective's honesty would end up forcing him to leave Erinsborough.

Brennan soon found himself losing friends at work, and slowly being targeted with other small acts of revenge, such as his car tyres being let down. And after a night of flirting, he and Jade ended up having a one-night-stand, which they both agreed to keep a secret, though Jade failed to see what all the fuss was about. Kate was given fresh hope that she and Brennan could get back together when he made a permanent move to Ramsay Street, sharing number 26 with Kyle and Jade, but when she accidentally overheard them arguing about their night together, she was horrified. Although she quickly managed to patch things up with Jade, who admitted that she had always struggled to keep friends, Kate found it harder to forgive Brennan for his lies. At work, things were no better for Brennan, as he found himself being harassed more and more and, just as he and Kate were finally getting close again, his boss, Superintendent Duncan Hayes, told him that he'd have to go into witness protection until the trial. With only a few hours' warning, Brennan prepared himself to pack up his life in Erinsborough, but decided that he had to tell Kate, and asked her to go with him. She agreed to go, and tried to persuade Sophie to leave with them, as Brennan organised things and was forced to tell Kyle what was going on when he caught him with his bags packed. At the meeting spot, Brennan waited for Kate, who, with Sophie, was running to try and meet him, but she missed the deadline and Brennan was driven out of her life for good.

A few weeks later, in his capacity as a lawyer, Toadie was at the police station with Hayes, when he overheard a conversation which led him to believe that Brennan had been killed. Toadie was asked to keep the information to himself, and it was some months before a devastated Kate finally found out what had happened.

A couple of years passed, and Kate was moving on with her life and in a new relationship with Mason Turner, when she thought she spotted Brennan in the distance, whilst watching a solar eclipse. After speaking to Toadie, Kate began to wonder if Brennan could really be alive, and she got her answer a few days later when he turned up on her doorstep. Kate finally found out about the threats to Brennan's life that had caused him to go into witness protection, and she explained how she'd wanted to go with him, but had been a few minutes late. Brennan told Kate that Wes Holland, the man who'd been after him, had died, so he'd been able to come out of hiding, but after returning to Erinsborough and seeing her, he wasn't sure how she'd react. However, after learning that she'd been asking questions at the police station about him, he'd decided to risk it, believing that she wanted to see him again. He told her that he'd been living in the Blue Mountains, and working as an abseiling instructor, and he also made it clear that he wanted Kate back.

Though happy with Mason, Kate realised that she still wanted to spend time with Brennan and try to find out more about his time away. After catching up with some of his old friends, including Lucas and Kyle, Brennan learnt from Paul that Kate's new boyfriend was a convicted criminal, who was currently up on charges for robbing Lassiter's. During dinner with Kate, Brennan admitted that Wes Holland had tracked him down and a fight had broken out, only stopped by the police killed Holland and leaving Brennan with a nasty scar from a knife wound. As they chatted, Brennan tried to make Kate see that her future was with him, rather than with a criminal like Mason, and when he dropped her home, they ended up sharing a kiss. Though Kate had already made up her mind to stick with Mason, there was another surprise to come when Mason overheard a call at the hotel, from Brennan's girlfriend Sienna, back in Sydney. Mason went to the school, where Kate was now working as a teacher, to tell her, but was surprised to find Brennan already there, and a fight broke out. Later, Brennan explained to Kate that he and Sienna were in a serious relationship, and he'd even been planning to propose, but he had to come and see Kate to find out where things stood between them, before he could move on with someone else. Kate then told him that, although she was happy to have seen him again and finally closed that chapter of her life, she had made the choice to be with Mason, and so Brennan once again left Erinsborough.

Nine months later, Brennan was back in Erinsborough in surprising circumstances, when he was travelling in the local area and found himself running into Mason. Mason had been camping with Amber, Imogen and Josh and, whilst abseiling, Josh had fallen and been badly injured. Brennan helped to contact the emergency services with his satellite phone, and then drove the kids to the hospital, as Josh was airlifted. There, he waited with them all and, once it was clear that Josh was out of danger, he decided to leave, only to run straight into Kate. He explained how he'd sold the abseiling school and had been travelling around the area for a few weeks, trying to figure out what to do next with his life, having broken up with Sienna. Kate was having problems of her own, but wasn't willing to discuss it. However, after running into a tearful Kate again, Brennan started to wonder if she needed him to stick around. And when he was then offered a job working at Fitzgerald Motors by new manager Danni, he decided that he might stay in Erinsborough for a while. Unable to throw off his past life as a detective, Brennan soon became suspicious when he noticed the CCTV cameras that had been installed at the garage, pointing out to Chris that they weren't much use as they were only pointing out the doors. And when Kate found out that Brennan was sticking around, she accused him of stalking her, as they turned up in all the same places and he rescued her from a guy hassling her in the bar. When they then became trapped in the lift at the hotel, and started chatting about their disastrous love lives, Brennan knew that the old spark was still there, so once they were freed, he began to make enquiries about taking over the lease for 24 Ramsay Street.

Not wanting to take on the whole house on his own, Brennan put up an ad for housemates in Harold's Store, and Kate soon spotted it and demanded to know what he was up to. He explained that he couldn't stay at the hotel and would need somewhere to live - and he pointed out that Kate didn't even live on Ramsay Street any more, now that she was staying with Paul at Lassiter's, so it shouldn't be a problem. Meanwhile, at work, Brennan was still trying to get to the bottom of the mystery of the CCTV cameras, and his suspicions grew stronger when Danni started behaving strangely when a customer with the name of Montague brought his car in. Danni then finally admitted that she was struggling to move on from an abusive ex, Stephen Montague, and when Chris and Brennan realised that she'd been sleeping in the garage, Brennan offered her one of his spare rooms, promising that she'd be safe with him. However, when Kate found out about Brennan's new living arrangements, she once again marched over to number 24, but this time, she suddenly planted a kiss on him, before quickly realising that she'd made a mistake and fleeing from the house. When Brennan caught up with her, Kate told him that she'd made a mistake and there was no chance of them getting back together. However, Brennan was certain that they could still have a future together if Kate was honest with him, and so he found her again later that week and asked her directly if she genuinely thought that they could ever be a couple. Kate was silent, and Brennan took that as his answer.

Still preoccupied with Danni's troubles, Brennan was suspicious when he saw a car parked outside the garage several times, and became convinced that it was Stephen Montague and that he was waiting to get Danni alone. Not wanting to worry Danni, Brennan confided in Chris and they tried to make sure that she wasn't left alone at the garage at any time. Unfortunately, she ended up there on her own later that day, when she went to get changed for a game of footy with the guys, and found herself cornered by Stephen. After Kyle tried and failed to get her to leave the garage, he reported back to Brennan that Danni was behaving oddly, and Brennan made it back to the garage just in time to stop Stephen from bundling Danni into his car. Stephen was taken away by the police, both for breaking his AVO and for attempted kidnapping, and a grateful Danni later attempted to kiss Brennan, who quickly made it clear that he wasn't interested. Meanwhile, Brennan was annoyed when he realised that Rebecca had returned to town, as she'd gotten away with pushing Paul from the Lassiter's mezzanine all those years earlier, and Kate's false alibi had caused huge problems, which their relationship had never recovered from. Though only in town briefly on business, Rebecca decided that she was going to stick around a little longer, and made it her mission to get Kate and Brennan back together and fix the mistakes of the past. Rebecca did her best to push Kate and Brennan together, but Kate confided in Rebecca that she'd been told that she could never have children, and, knowing that Brennan had always wanted kids of his own, she was just saving them both from a lot of heartache. It wasn't long before Brennan learnt this information for himself - from Kyle - and he finally realised why Kate had been acting so oddly. He tracked her down and made it clear that he still wanted to be with her, suggesting that they could adopt, but Kate knew that it wouldn't be the same and that he'd end up resenting her. Paul, meanwhile, was furious to see his niece once again in tears over Brennan, and told him that he was going to do everything in his power to make sure that he and Kate could never be together.

After the emotions of the previous week had died down, Kate visised Brennan, telling him that if he was determined to stick around in Erinsborough, then he had to know that there was no chance of them getting back together. Brennan attempted to move on, helping out with the Erinsborough Farm Day fundraiser and supporting Danni when she learnt that Stephen had been given bail. But his mind was always on Kate, and when he found out that an intruder had been spotted outside number 24 - where Kate had just gone in order to find a sweater for Danni - he rushed home, only to find that the intruder was actually his ex, Sienna. Not entirely sure of how, or why, she'd broken into his house, Brennan told Sienna that he wasn't interested in getting back together with her and she was wasting her time. She, however, wouldn't take no for an answer and it didn't take her long to work out that Kate was the ex that Brennan had been hung up on for so much of their relationship. Sienna then visited Kate in the penthouse apartment she shared with Paul, and told her to back off - Kate made it clear that she and Brennan hadn't been a couple in a long time, and wouldn't be getting back together. A desperate Sienna asked Kate to make that clearer to Brennan, as she was the only thing standing between them getting back together.

The following day, Sienna finally seemed to accept that Brennan didn't want her back and she left town. At the same time, Kate came to the realisation that she'd been allowing her fertility problems to rule her decisions for too long, and that Brennan made her happy, so they should be together. Brennan was delighted by this decision, but Paul was furious, still feeling that Brennan was no good for his niece. When Paul caught Kate and Brennan kissing on the couch, he made it clear that Brennan wasn't welcome in the apartment, but was shocked when Kate said that, if that was the case, then she'd have to move out. With Kate now staying at number 24 too, Brennan was alarmed when Chris spotted Stephen Montague in Erinsborough. Chris caught him breaking into number 24, but he managed to get away, and so Danni decided to leave town for a while, going to stay with a friend in Adelaide. With the house to themselves, Brennan and Kate were more lovey dovey than ever, with all but Paul happy to see them so blissfully in love. As Brennan started to make plans for a gathering at number 24 to celebrate Kate's birthday, Paul decided to try to outdo him, organising a big party at Charlie's and inviting Sophie down from Sydney. Brennan seemed unfazed as he realised what Paul was up to, as he was planning a big surprise of his own - a marriage proposal!

As Kate's birthday arrived, Brennan surprised her with a romantic breakfast, only for her to toss out the glass of champagne - which had the engagement ring in the bottom - when a fly landed in it. As Brennan rethought his proposal plan, he was surprised by a text message from an anonymous number, which claimed that someone was watching him. Later, Sienna made a surprise reappearance in Erinsborough, and Brennan had to again tell her that he wasn't interested in getting back together, with her warning that she'd never forgive him. Following that difficult morning, things soon picked up when Brennan proposed and Kate happily accepted - only for a gunshot to ring out. Kate slumped in Brennan's arms and he carried her to the Lassiter's complex as the paramedics arrived, but she was unable to be saved. As Stephen Montague had been spotted in Erinsborough that day and had apparently attacked Chris and left him in hospital, he became the prime suspect in Kate's shooting, but a few days later, as the residents of Ramsay Street prepared to say a final goodbye to Kate at her funeral, the police were no closer to tracking down Montague. Following a passionate speech at the funeral, Brennan was standing by Kate's grave later that day, when a devastated Paul tracked him down and made it clear that he blamed Brennan for the shooting, as the ex-detective was a more likely target for the bullet than an innocent school teacher.

Brennan soon became obsessed with catching Kate's killer, certain that it was Stephen Montague, as he was nearby at the time, and had motive to want to harm Brennan. But with Montague nowhere to be found, and the police drawing a blank - and tiring of Brennan's constant badgering - he decided to find a way to flush Montague out of hiding. After telling Danni that she was safe now, Brennan managed to get her to come back to Erinsborough, but then admitted that he needed her help to reactivate her Facebook and Twitter pages, in the hope that Montague would see them and come back for her. The plan failed when Danni refused to put herself in danger like that and instead left town again, so Brennan decided to scan in a photo of Danni and make a new Twitter page for her, hopeful that he could still catch out Montague and get some justice for Kate. The following week, Danni got in touch with Sonya to tell her about the fake Twitter page, and Sonya immediately realised who was responsible. Brennan claimed that he was going to back off, but he then drove Danni's car back to Ramsay Street, parking it outside the house so that Montague would see it. Montague then broke into 24 Ramsay Street, demanding to know where Danni was, and holding Brennan and Imogen - who'd been cooking food for Brennan and had developed quite a crush on him since Kate's death - as hostages. Brennan eventually managed to lock Imogen in a cupboard before Montague could take her away, and a fight broke out between the two men, with Montague managing to get away into the neighbouring gardens.

With the street on lockdown and the police searching all of the houses, Brennan was stopped from going back inside, but managed to sneak away when an argument broke out between the police and Sonya, who was desperately trying to find Callum. Callum had actually been in the back garden at number 32, labelling up Lou's home brew, and had been trapped in the shed by a desperate Montague. Callum then persuaded Montague that they should go into number 30, and he could hide in the roof until the police had gone. Montague fell for it, but once inside, Callum hit him over the head and ran out of the house, shouting to the police. Brennan heard what was going on and managed to get inside before the police, grabbing Montague around the throat. Having failed to get a confession out of him across the street, Brennan tried again to get him to admit to shooting Kate, but the police then came in and pulled the two men apart. As the police questioned Montague and charged him with breaking his bail, Brennan waited and was eventually told that Montague had an alibi for the time of the shooting, which was backed up by his priest and by CCTV footage, so couldn't possibly have been the person who shot Kate. In the wake of these revelations, Danni returned to town, but quickly realised that she could no longer stay in Erinsborough and so she made the decision to leave town permanently. Brennan, meanwhile, became more obsessed than ever with figuring out who had shot Kate, and managed to get hold of illegal copies of the files from the murder investigation, desperate to find something that the police had missed.

The following week, another suspect emerged when Tracey Wong - a private detective hired by Paul - found out that Sienna had lied about her alibi, and had actually been at Lassiter's hotel, just thirty minutes before the shooting took place. She returned to Erinsborough, and Brennan took her to the police station where she admitted that she'd lied about being with her cousin that day, and that she'd actually been having a drink at Lassiter's, before getting a taxi to the airport. As she'd paid for the taxi with cash, she was unable to prove it, and she explained that she'd only lied because she didn't want to be a suspect, knowing how bad it looked for her. Whilst Brennan stood by Sienna, certain that she'd wouldn't be capable of killing anyone, Paul was furious that she was able to just change her statement and walk away, and he decided to put the pressure on her, leaking her story to the Waratah Star. Sienna then claimed that her bosses had seen the story online and she'd been fired, and that her roommate was worried and had asked her not to come back. Brennan agreed to let Sienna stay, despite the concerns of his friends and neighbours, unaware that Sienna was lying to him and was just trying once again to win him back.

As they fell into a familiar routine of living together, Brennan and Sienna seemed to be getting along well, until he realised one morning at breakfast that he hadn't even thought about Kate that morning. Feeling terrible, he shut himself off from Sienna, until she made him be honest about his guilt. Grateful for Sienna's support, Brennan ended up kissing her, but quickly made it clear that it was a mistake. He fled from the house, but returned later and told Sienna that it might be for the best if she moved out. Claiming that she had nowhere else to go, Sienna begged him to reconsider, and he eventually told her that she could stay, but the kiss was a one-off and would never, ever happen again. Sienna agreed, and offered to give him a few days on his own, during which she would return to the Blue Mountains and collect the last of her things. When Brennan then found a note amongst Kate's thing, with the words 'You're going to pay' written over and over, he immediately recognised the handwriting and notepaper from one of Sienna's shopping lists. When she returned, he calmly tried to find out if she'd been lying to him all along, but eventually blurted out the accusation that Sienna had been the one who shot Kate. She continued to deny this as she was taken in for more questioning, and Brennan decided to do some work of his own to try and find the taxi driver, who Sienna claimed had taken her to the airport that day. The police, along with Brennan, eventually found the man, who had been keeping a low profile during the initial investigations as he was working on an expired visa, but Sienna's story was found to be true and she was eliminated as a suspect. Though relieved that Sienna wasn't responsible, Brennan told her that it would be best if she left Erinsborough, and realised that once again, the investigation into Kate's murder had hit a dead end.

Fearing that Kate's killer would never be found, Paul decided that he and Brennan needed to team up, and he suggested that they could start by trying to get hold of the files on the case that had seen Brennan put into witness protection. Brennan was disgusted at Paul's idea to break into the building where the documents were stored, but eventually agreed to try and get access in as legal a way as he could. However, when that plan failed, Brennan managed to sneak in and, after almost being caught by a security guard, he found the files he was looking for. But after a change of heart, he put the files back without reading them, later telling Paul that he wouldn't be able to live with himself - and it wouldn't be what Kate wanted him to do, either. Brennan soon found himself caught up in another dilemma when he arrived at The Waterhole, only to find that it was singles' night. He was talked into staying, but soon found himself targeted by Imogen, and he was finally forced to make it clear to her that, even if he was able to move on one day and find a new girlfriend, it would be someone closer to his own age, and not a teenager like her. He then headed to Harold's Store, where he found Honor Taylor, a woman who'd been on her way to the singles' night and was trying to fix her shoe. Brennan helped her, and they soon got chatting about their shared love of Doctor Who, but as the store started closing up for the night, Brennan felt guilty about how comfortable he'd been in the company of another woman, and told a confused Honor that he had to go.

After finding a new housemate in the form of free-spirited, but secretive, Paige Novak, Brennan also learnt of a new lead in Kate's murder case. CCTV footage had been found showing Victor Cleary burying something in the mulch at Kyle's builder's yard. The police eventually found it, as the mulch had since been distributed to several places in the area, and realised that it was the gun that had been used to kill Kate. Victor had a motive too - he was the younger brother of Gus Cleary, who'd died in 2004, and whose murder Paul had confessed to a few years later. Brennan was furious that, after weeks of thinking someone had killed Kate because of him, it actually all led back to Paul. It wasn't long before Brennan realised that Paul had been communicating with Victor, leaving notes for each other at Kate's grave, and that Paul had obtained a gun for one final showdown with Kate's killer. After informing Matt, Brennan waited for the police to act, but when Paul managed to get out of the hotel without the police spotting him, Brennan tagged along on their search, and managed to stop Paul just in time, as he reached for the gun during his confrontation with Victor. At the police station, Victor confessed to killing Kate and asked to see Brennan and Paul - he apologised to Brennan for what he'd done, and asked him to make sure that Paul never forgot that he'd killed Gus and that was why Kate was dead too. Brennan then started pestering the police about re-opening the investigation into Gus' death, and they finally agreed to bring Paul in for questioning. However, given Paul's fragile mental state, Matt told Brennan that there was no point in speaking to him. Paul, however, was finding it very difficult to live with his guilt and he asked Brennan to come and see him, before handing him a written confession to Gus' murder. After mulling it over and speaking to Terese - who pointed out that Paul was probably suffering enough - Brennan agreed that he'd drop the matter and that they could all begin the process of moving on from what had happened.

As he attempted to get his life back on track and spend more time with his friends, Brennan found himself with another new housemate when, following a huge fight at number 26, Naomi Canning found herself homeless. With two chaotic women under his roof, neat freak Brennan struggled to cope, but he quickly realised that Paige had some big problems of her own, and that his nagging about the cutlery drawer was only making matters worse. Brennan took Paige down to the garage to so some panel beating, hoping that it would release some of her tension - the plan worked, but Brennan was unaware that Paige was actually the long-lost daughter of two of the neighbours, Brad and Lauren, and was waiting for the right moment to reveal her true identity. As Paige's odd behaviour confused the neighbours and won her very few friends, Brennan proved to be a great support, as he continued to help her to deal with her stress. He was there for her when she was finally revealed as Brad and Lauren's daughter and was questioned by the police over the trashing of Harold's Store, and it started to become obvious to other residents of Ramsay Street that there was an attraction growing between Brennan and Paige. But when they started to point this out to Brennan, he started to get cold feet, and when Brennan lost a bet and had to take Paige out for dinner, he stood her up. He then did his best to avoid being alone with her, as Ramsay Street prepared itself for a huge storm, but when they were finally left alone in the house, the tension boiled over and they kissed.

With Brennan still struggling with memories of Kate, he was reluctant to turn it into anything serious, though Paige was beginning to fall hard for him. When she turned up for one of their dates in a dress that had once belonged to Kate, which she'd found in a local second-hand shop, Brennan reacted badly, and although he and Paige then managed to sort out their feelings and make a go of things, her jealousy quickly caused problems. After becoming suspicious of newcomer Dakota Davies, Brennan contacted Federal Agent Greta Jackson, who he knew from his time in witness protection, who found out that Dakota's former employers had connections to diamond smuggling cartels. Greta asked Brennan to work undercover and try to find out what Dakota was up to. As he attempted to get closer to her, she ended up kissing him, witnessed by a shocked Paige, who ended up dumping a drink all over Dakota's laptop in revenge. When Paige then finally found out the truth, she was left embarrassed and Brennan realised that maybe the relationship wasn't working. Paige then moved out of number 24, but continued to hope that she and Brennan might get back together, and was left upset as she realised that he viewed the relationship as a mistake, and had no intention of getting back together with her. As Naomi had also moved out and returned to the Canning house, Brennan then found himself alone at 24 Ramsay Street.

Soon after, Brennan attempted to crack another case when Sonya was targeted by a series of poison pen letters, which Toadie was trying to keep from her. Brennan helped Toadie to narrow down the list of suspects, and offered support to Sonya until it was finally revealed that her old friend Erin was behind the hate campaign. Erin and Sonya had both suffered from addiction problems when they were younger, and had both lost custody of their own children, but whilst Sonya had managed to get her life back together and Callum had become part of her life again, Erin was still an addict and had lost daughter Cat to the foster care system. Brennan was surprised when Sonya, feeling guilty about the direction that Erin's life had taken, paid her bail, but Erin was ungrateful and disappeared. Brennan then managed to track her down to a squat where she'd become ill, and offered to help her after she was diagnosed with a chest infection, giving her somewhere to stay. However, despite everyone's best attempts to help Erin reunite with Cat, she struggled badly with the situation and ended up stealing Brennan's wallet, phone and watch, before doing a runner. Brennan soon had another unexpected houseguest, however, when his younger brother Tyler arrived in town. Tyler called Brennan to pick him up from the police station after he'd been involved in a fight, and his timing couldn't be worst, as he interrupted a passionate moment between Brennan and Naomi - she had since moved out of number 24, though the pair had recently been flirting a lot with each other. Brennan was surprised by Tyler's unexpected arrival, and his younger brother explained that he'd come to apply for the mechanic's position at Fitzgerald Motors, meaning that the brothers would be working side by side. Brennan admitted to Toadie that he wasn't sure about the idea, as he hadn't been very close to his parents or his siblings in a long time, and Tyler had never been very reliable. Toadie then pointed out that maybe it was time to start making an effort, and so Brennan told Tyler that he could stay, and was welcome to apply for the job.

Brennan then made the decision to apply for a return to the police force, as he'd been unhappy for a long time with the way he'd seen cases being dealt with. Though Naomi was supportive, Tyler was very uncomfortable with the idea - Brennan believed that it was because of his previous stint in witness protection, when the family had believed that he was dead, but Tyler's reluctance was actually because he'd become caught up with small-time criminal Dennis Dimato, helping to strip stolen cars. As Tyler was getting in deeper with Dimato, Brennan uncovered another connection when he found out that his colleague Matt Turner had been working for Dimato and, his family in dire financial problems, had accepted bribes to keep quiet about the illegal activities he'd witnessed. Brennan agreed to keep quiet, suggesting that Matt take long service leave from work, but warning him that he might have to give evidence against Dimato at some point in the future. Still unaware of his little brother's involvement in criminal activities, Brennan became part of a sting operation, with tracking devices placed in cars, one of which was then stolen. Unaware that Tyler was the driver of the stolen car, Brennan and several other officers swooped on the container yard and arrested Dimato, with Tyler only narrowly avoiding being caught too. Dimato was released a few days later on bail, and had soon bought the garage, leaving Tyler trapped doing his dirty work, and Brennan was furious as Dimato then skipped the country, leaving him more determined than ever to bring the criminal down.

Meanwhile, Brennan's relationship with Naomi seemed to be going from strength to strength, and although they agreed to give things a proper go, neither of them was quite ready to use the 'l' word. But as everything seemed to be going well, and even Sheila was happy with her daughter's latest relationship, Brennan was unaware of just how close Naomi was getting to her new boss, Paul. As Paul had just been diagnosed with leukaemia - unbeknownst to him and Naomi, it was a fake diagnosis by twisted oncologist Nick Petrides in a desperate attempt to convince Paul to help fund a cancer research centre - Naomi had been trusted with keeping it all a secret, and had been spending a lot of time with Paul and had seen him at his most vulnerable. After sharing a kiss with Paul, Naomi realised that she was developing feelings for him and strongly believed that it was mutual. Struggling to tell Brennan the truth, the final straw came when he was stuck at home suffering from a nasty cold and, seeing what a terrible patient he was, and how bravely Paul had been dealing with his own treatment, Naomi shocked Brennan by telling him that things were over between them.

Trivia Notes
• Mark's passport (shown in episode 6195) had Jack and Elaine Brennan listed as his emergency contacts. Kate telephoned one of them saying she was a friend of their son, but it has not been clarified if one or both are Mark's biological parents. Jack and Elaine's address was 56 Fidel Lane, Moonee Ponds. Their telephone number was 03 985556
• In 2015, when Tyler first arrives, Mark tells Toadie that he also has another brother, as well as a sister, and that their father tried to get all four of them interested in turning mechanics into a career. Mark also mentions to Tyler that he should go and visit 'Aaron' who works in the mines - this is presumably their other brother, though it is not explicitly stated
• Kate dreamt about Mark shortly after his 2011 departure; the figure in the dream had his back to Kate. He was played by Mathieu Gonzalez and credited as "Brennan Lookalike"
• Brennan is a Doctor Who fan; he asked Zeke to bring him back a Tardis when he went to London, and he also used the name 'Matt Smith' (the actor who was playing the Doctor at the time) when in witness protection
• Before working for Erinsborough police, Brennan worked in West Waratah, where one of his colleagues was Kelly Merolli