After local businessman Paul Robinson is pushed from Lassiter's mezzanine, Mark is placed in charge of the investigation. He goes to the crime scene and then to the hospital to speak with Paul's wife, Rebecca. Mark learns Paul made several enemies before the attempt on his life and Diana Marshall becomes the prime suspect. Mark questions several Erinsborough residents, including Paul's son, Andrew, and Kate Ramsay, who gives Rebecca an alibi. When Andrew tries to help the investigation along, Mark warns him not to try and do his job for him. Paul wakes up from his coma and implies that Diana pushed him. She flees the country. Weeks later, Mark asks Kate out to dinner and after initially turning him down, she agrees. Their date is interrupted by Declan and Kate leaves. Declan and Mark later fight over Kate, but she is only interested in Mark. After Kate confronts Mark about making threats towards Declan, they break up. Kate learns Declan was lying and she apologises to Mark. She kisses him in front of his colleagues, making him realise that she is worth the risk. Mark tells Kate that he needs to solve Paul's case to prove himself to his superiors, but he decides that he does not want to sacrifice their relationship and he gives up the case. Lucas Fitzgerald admits to Mark that he is involved in illegal races, and Mark goes undercover to catch the gang. Mark eventually catches the ringleader of the illegal races,
Garland Cole (
Jack Finsterer), after he asks Lucas to rebirth some cars for him. After Rebecca admits to pushing Paul, Kate confesses to giving her a false alibi. Mark breaks up with her, but he becomes jealous when it appears she is moving on with Kyle Canning. Mark briefly moves in with Toadfish Rebecchi, when his home has to be fumigated, and becomes a role model to his son,
Callum (
Morgan Baker). Kyle turns to Mark for help when he is blackmailed by corrupt policeman Wes Holland. Mark does not initially believe Kyle, but after seeing Holland taking a bribe, Mark arrests him. Some of Mark's colleagues turn against him. He has a one-night stand with Jade Mitchell and Kate struggles to forgive him. Mark is targeted with small acts of revenge for arresting Holland. Things escalate and Mark is asked to go into witness protection until the trial. Mark asks Kate to go with him and she agrees. However, she misses the deadline and Mark leaves without her. Shortly afterwards Toadie overhears a conversation at the police station and learns Mark has been killed. He is forbidden from telling anyone, but ultimately convinces the superintendent to tell Kate, who is heartbroken. Two years later, Mark returns to Erinsborough. He tells Kate that Holland has died, so he was able to leave witness protection. Mark explains that his death had to be faked after Holland put out a hit on him. After learning that Kate had been asking about him, he believed that she wanted to see him again. Mark explains that he has been living in the Blue Mountains and working as an abseiling instructor. Mark and Kate spend time together, which makes her boyfriend, Mason, jealous. Mark also catches up with Lucas and Kyle. He tries to persuade Kate that her future is with him and they kiss. But when Mason learns Mark has a girlfriend in Sydney, he tells Kate, resulting in a fight between himself and Mark. Mark tells Kate that he was going to propose to his girlfriend, but wanted to see where things stood between them first. Kate chooses Mason and Mark leaves. Months later, Mason runs into Mark in Lysterfield, where he asks for his help as
Josh Willis (Harley Bonner) has been injured abseiling. Mark accompanies the group to the hospital, where he runs into Kate. Mark decides to stay in Erinsborough and is offered a job at Fitzgerald Motors by
Danni Ferguson (Laura McIntosh). He also moves into Number 24. Danni confides in Mark that is struggling to move on from her abusive ex-partner,
Stephen Montague (
Damian Hill), and Mark invites Danni to move in with him. He later saves her from being kidnapped by Stephen. Mark asks Kate for another chance, but she turns him down and Paul warns him to stay away from her. Mark's ex-girlfriend
Sienna Matthews (
Sarah Roberts) tries to win him back, but Mark reunites with Kate. Paul disapproves of the relationship, so Kate moves in with Mark. Sienna returns once again to try and win Mark back, but he rejects her. Mark proposes to Kate on her birthday and she accepts, but shortly after, she is shot and dies. Paul blames Mark for Kate's death. Believing Montague is responsible, Mark lures him out of hiding by using Danni as bait. Montague breaks into Mark's house and holds him and
Imogen Willis (Ariel Kaplan) hostage. After Mark tackles him, Montague escapes and is caught by the police. Mark then learns that Montague had an alibi for the time of the shooting. Sienna is also questioned as she gave a false alibi. Mark lets her stay with him. Sienna kisses him, but soon apologises. Mark discovers a threatening note from Sienna to Kate and she is questioned by the police again. A taxi driver backs up Sienna's alibi and she leaves. Paul asks Mark to steal some police files, hoping to find a lead in Kate's case, but Mark decides against it. Mark witnesses Paul buying a gun and he and
Matt Turner (
Josef Brown) stop Paul from shooting
Victor Cleary (Richard Sutherland), who confesses to shooting Kate in revenge for Paul killing his brother
Gus (Ben Barrack). Paul gives Mark a written confession saying he killed Gus, but Mark does not hand it to the police. Paige Smith moves in with Mark, and he helps her when she is revealed to be the secret daughter of
Lauren Turner (
Kate Kendall) and
Brad Willis (
Kip Gamblin). Mark and Paige begin a relationship, and Paul accuses Mark of moving on from Kate too quickly. Mark is asked to get closer to
Dakota Davies (
Sheree Murphy) and use her interest in him to investigate her. Mark and Matt lead a police raid on Dakota's business and find she is smuggling diamonds, however Dakota gets away. Mark and Paige realise that he is not as committed to the relationship as she is and they break up. Mark supports
Sonya (
Eve Morey) when she becomes the victim of a poison pen letter campaign. Sonya's stalker,
Erin (
Adrienne Pickering), breaks into Sonya's house and knocks Mark unconscious. Both Mark and Sonya try to help Erin. Mark convinces her to go to the hospital after she falls ill and invites her to stay with him temporarily. Mark grows closer to
Naomi Canning (
Morgana O'Reilly) and helps her out when she is threatened by
Dennis Dimato (David Serafin). Mark's younger brother,
Tyler (
Travis Burns), gets a job at the garage and he moves in with Mark. In an effort to bring down Dimato, Mark rejoins the police force, but has to start back as a constable. After assuring Naomi that he does not have feelings for Paige, they declare themselves an official couple. Mark learns Matt has been accepting bribes from Dimato and Brennan agrees not to tell anyone if Matt takes long-service leave and gives him a statement about Dimato's operations. Matt dies after being involved in a hit-and-run and Brennan attacks Dimato when he turns up to Matt's wake. He uses Matt's information to set up a police sting to catch the thief stealing cars for Dimato. The police follow a stolen car back to Dimato and Brennan arrests him. Brennan and Naomi's relationship suffers when she becomes Paul's executive assistant. Brennan asks Lauren if he can expose Matt's corruption to put Dimato in prison, which causes her son,
Bailey (Calen Mackenzie), to lash out at him. Naomi breaks up with Mark and he learns that she has feelings for Paul. Her mother
Sheila Canning (
Colette Mann) tries to reunite them as she disapproves of Paul, while Paul decides to help Mark win Naomi back. He succeeds, but she discovers that Paul has been helping Mark out with their dates and ends their relationship. Mark shows an interest in Paige, but discovers she is dating Tyler. He later learns that this is a ruse to cover up their involvement with Dimato, who has bought the garage. They eventually regain Mark's trust after helping to bring Dimato to justice, and Mark and Paige reunite. Mark and Tyler's brother
Aaron (Matt Wilson) comes to stay with them, and they are later joined by their father
Russell (Russell Kiefel), who has a strained relationship with his sons. The Brennans consider buying the garage together, but Tyler later reveals that Russell abused him when he was younger. Mark and Aaron support Tyler and force Russell to leave. Mark and Paige discuss their future together when he admits that he is ready to have children, while she is not. Mark asks Tyler to buy Number 24 with him. They brothers fall out when Tyler learns that Mark tried to protect Aaron from arrest during his investigation into the Erinsborough High fire. While discussing their future, Mark and Paige get engaged. Mark is deeply critical of Paige when she befriends Dimato's lover
Michelle Kim (
Ra Chapman), who claims to be on the run from Dimato. The issue divides Mark, who does not trust Michelle, and Paige, who believes Mark thinks she is naïve. On their wedding day the police find stolen items with Paige's fingerprints on them, and Mark arrests her. She explains that Dimato and Michelle were trying to set her up and that Paul helped her deal with the situation, and that she did not tell Mark to protect him. Furious at Paige for further lies after promising there would be no secrets between them, Mark calls off the wedding. He later apologises and tries to convince Paige to take him back, but she refuses, wanting to find direction in her life and believing they are too different. Mark befriends
Stephanie Scully (
Carla Bonner), and they share a kiss, before deciding to remain friends. After a jealous Paige fights with Steph, Mark and Steph have sex and begin a relationship. Following an explosion at Lassiter's Hotel, Mark finds evidence Paul was responsible and arrests him. Released on bail, Paul convinces Steph of his innocence, causing trouble in her and Mark's relationship. Tyler is later questioned and Mark is removed from the case. Mark raises the subject of having children with Steph and she tells him she is open to the idea of having a child with him in the future. Mark starts to think Paul could be innocent, but is threatened with dismissal if he continues to investigate. He later discovers that
Jacka Hills (Brad McMurray) caused the explosion on
Julie Quill's (Gail Easdale) orders. Mark investigates the release of snakes in Ramsay Street and soon realises that Steph is being stalked. Hearing that someone has made a confession to Father
Jack Callahan (
Andrew Morley), Mark bugs the confessional, despite being ordered not to. Mark learns from Steph's former girlfriend
Belinda Bell (Nikki Shiels) that one of her patients
Ari Philcox (Dylan Watson) is behind the release of the snakes. Mark is suspended when the bug is discovered. Despite this, Mark goes after Ari when he threatens Belinda and Steph's son
Charlie Hoyland (Alexander McGuire), but he is stabbed in the process. His injuries are not life-threatening. Steph and Mark are saddened when Charlie has to return home, and decide to have a child together. However, Steph fears that her mental health problems will return and Sonya offers to be their surrogate. When they learn that Steph has a low ovarian count, Steph ends the relationship, until Mark convinces her to try the IVF procedure once.
Victoria Lamb (Claudia Greenstone) then informs them that are not able to collect any viable eggs, so Sonya also offers to be an egg donor. The fertilisation goes ahead, but Steph has second thought and asks Mark and Sonya to end the process. Mark proposes to Steph and she accepts. Shortly after, Sonya announces she is pregnant. Mark begins spending more time with Sonya, making Steph feel left out. Steph ends her relationship with Mark after she develops feelings for Victoria. Mark and Sonya learn they are having a girl, but Sonya later suffers a miscarriage. While they are grieving together, Mark develops feelings for Sonya and they kiss, but Sonya tells him she wants to remain friends. Mark tampers with evidence when it becomes clear Sonya caused is responsible for a car accident at the Erinsborough Backpackers'. Mark visits Paige in Queensland and they kiss, but Paige rejects him when he declares his feelings for her. Mark begins spending time with
Elly Conway (
Jodi Anasta) and they develop a relationship. Mark, Aaron and Tyler's mother
Fay Brennan (
Zoe Bertram) comes to visit. She tells them that their father has been in contact and Aaron encourages her to see him. A couple of weeks later, Fay tells her sons that Russell has suffered a heart attack and wants to see them. But shortly before they are due to depart, Russell dies. He leaves Mark his fishing rods in his will, but leaves Aaron and Tyler his boat. Sheila then tells Mark, Aaron and Tyler that Fay had an affair and one of them is not Russell's son. Fay returns and tells Tyler his father is actually
Hamish Roche (Sean Taylor), who arrives in town shortly after. Mark encourages Tyler to bond with Hamish. Elly breaks up with Mark upon learning Paige has feelings for him. Hamish goads Mark into losing his temper in front of Tyler, and Mark suspects that Hamish is trying to turn Tyler against him. Hamish and Mark get into a scuffle on the boat, and Hamish falls and hits his head on the deck. Tyler tells his brother to get his anger issues under control. Mark and Paige get back together. Mark is called to the hospital to find a contact for nurse
Louise McLeod (
Maria Theodorakis), who is in a coma. He begins to suspect that there is a link between her and Hamish. Hamish makes a complaint to Mark's superior that he is harassing him, and Mark is taken off the case. Mark asks Fay to return to Erinsborough and she reveals that Louise was Russell's nurse and is suspected of causing his death. Hamish's body is found floating in the spa at Number 26 and Tyler admits that he hit his father with a garden gnome, but Hamish was still alive when he left. Mark goes to the evidence locker and wipes Tyler's fingerprints off the gnome. After admitting to tampering with evidence in Sonya's investigation and Hamish's murder, Mark is suspended from the police force. Paige's son
Gabriel Smith (Kian Bafekrpour) is kidnapped by Louise and she tells Mark to bring her money and a passport for his safe return. Gabe's father, Jack, calls the police and Louise is arrested. Gabe is later returned to Number 24 anonymously. Jack punches Mark during an argument about Gabe. Tyler is sentenced to 20 years in prison for Hamish's murder. Mark accepts a job at the garage. Paige wins a
glamping in a raffle and she and Mark arrive at the camp to find Jack and Steph there. Mark plans to propose to Paige, but she admits that she had sex with Jack. Mark later ends their relationship, and he struggles to be around Paige and Jack. Both Mark and Jack agree to help
Yashvi Rebecchi (Olivia Junkeer) with her football training, but when Mark kicks a football towards an inattentive Jack, it hits Gabe's pram, which falls into the lake. Gabe is fine and Mark apologises. Mark almost has sex with
Izzy Hoyland (
Natalie Bassingthwaighte), but they are interrupted and he leaves. He later kisses Elly, but she knows that he is not over Paige and he apologises. Mark and Aaron's sister
Chloe Brennan (
April Rose Pengilly) arrives for an extended visit and hopes to reconnect with her brothers. Mark makes his peace with Paige, before she and Jack leave Erinsborough. Mark and Elly resume dating, and their relationship slowly becomes more serious. When Chloe reveals that she has
Huntington's disease, an incurable hereditary disease, Mark is tested but learns he does not have the condition. Elly proposes to Mark, who accepts, and they begin planning their wedding. With Elly's support, Mark contests his suspension from the police force, using his grief at Caitlin's death to explain his past misconduct. Weeks before his wedding, Mark learns Sonya has been diagnosed with stage four
ovarian cancer. Broken by the thought of losing someone else, Mark pushes Elly away, considers calling off the wedding and begins visiting Kate's grave. The news of Sonya's sudden death causes Mark to have a panic attack. He decides to leave town for a few days, but later sends Elly a text calling off the wedding. Aaron finds Mark in the outback and persuades him to return. Mark tells Elly he loves her and they marry. However, during the reception, Mark finds Elly crying outside and she admits that she cheated on him with Chloe. Mark's relationships with Chloe and Aaron, who knew about the affair, are strained. He gives Elly his wedding ring back. When Elly tells Mark that she is pregnant, he allows her to move back in, but struggles to be intimate with her. Mark misses Elly's ultrasound appointment, but later sees her holding a picture of a baby and assumes that it is theirs. Elly later tells Mark that he is not the father of her baby, and the ultrasound image belongs to Caitlin. Mark ends their marriage and files for an annulment, which Elly does not contest. Mark and Chloe eventually reconcile when she turns to him for advice about
Pierce Greyson (
Tim Robards). He struggles when she and Elly later go on a date and admits to feeling replaced when Chloe accompanies Elly to an ultrasound appointment. Mark investigates the theft of money from
Leo Tanaka's (Tim Kano) Back Lane Bar bank account, but doubts the money will be recovered. Leo's business partner
Roxy Willis (Zima Anderson) is frustrated by lack of progress in investigation and berates Mark when he comes to the bar to celebrate his birthday. Later that night, Roxy comes to apologise to Mark and they have sex. They continue a casual relationship in secret. Mark learns Pierce has children and urges him to tell Chloe, who has reunited with him. Mark and Roxy's relationship is exposed when she drunkly kisses him during a party for Sheila. Mark breaks up with Roxy, but later gets drunk and apologises for letting the opinions of others affect him. He also rejects Chloe and Aaron's attempts at an intervention. Mark is uncomfortable with Roxy's behaviour during a date and admits he is used to more conservative dates. Roxy tries changing her image for their next date, but Mark insults her and says that he could never be in a relationship with her. Chloe tells him off for hurting Roxy, so he takes her flowers and apologises, but Roxy ends things between them for good. Mark later tells Chloe that he feels lost. The Brennans learn that Fay has gone missing, but she soon turns up at Mark's door, where they learn that her Huntingtons has progressed and she needs 24-hour supervision. Chloe considers moving to Adelaide, but Pierce tells Mark that seeing Fay deteriorate will be a preview of Chloe's future. The family go to Adelaide and on their return, Mark decides to move there to help Tyler take care of Fay. Not wanting to make face to face goodbyes, Mark records several video messages for his friends and family. He later visits Sonya's memorial bush at Lassiters, where he shares a goodbye with Elly. Six months later, Mark is temporarily seconded back to Erinsborough. While he is in town, he is reunited with Paige, who has returned amidst relationship problems with Jack. When they break up, Mark admits to Aaron that he still has feelings for Paige. The former couple continue to reconnect, but Mark is abruptly called back to Adelaide. However, Paige declares her feelings for him and he decides to stay so they can begin dating again. Despite their concerns about living in different states, their romance progresses fast and Paige proposes to Mark so they can get married as part of the Lassiter's wedding expo. After they marry, Jack tells Mark and Paige that he has accepted a priesthood in Adelaide, meaning Paige and Gabe can move to be with Mark and his family. Mark investigates
Finn Kelly's (
Rob Mills) death and is concerned when Elly comes under suspicion. Aware that the case is stacked against his ex-wife, Mark decides to stay on longer in Erinsborough to help Senior Detective
Sky Mangel (
Stephanie McIntosh) with the case. After noticing that his brother-in-law,
David Tanaka (
Takaya Honda), is struggling to deal with Finn's crimes, Mark gives him access to transcripts of Finn's video diaries, in which he talks about his returning memories and feelings. Sky finds out and reprimands Mark. He later discovers that Chloe has copied the videos onto a USB stick and given it to Elly behind his back. Paige contacts Mark to tell him that she is pregnant and he is delighted that he is finally going to be a father. He and Paige later hold an official wedding in Adelaide, which is attended by his family. At the end of the year, David and Aaron receive news that Paige has given birth to a son, whom she and Mark have named Freddie. ==Other appearances==