Mark Gray is the twin brother of Luke and adoptive son of Lily Gray. Mark had/has a crush on Emma Hill but currently unknown after Emma touched Mark when he was haphephobia, the fear of being touched. Mark is more friendly and calmer than his brother Luke. Luke was killed in the end of Season 2 and his body was carried by Mark to Andrew Sharp in a car.
Mark and Luke were born to a woman named Hilda Barkov, a Russian housekeeper for Lily Gray's father, who died while giving birth to the twins. Lily is their illegitimately adoptive mother.
During the gap between 2013 and 2014, Mark reveals to Ryan that he had been tailing him during his AA meetings via orders of his mom.
Mark is first introduced with a Carroll mask on, along with Luke and Carlos killing 5 people on the train station. This was an attempt to lure Joe out of hiding.
The twins, Mark and Luke, break into the home of a couple with a young child. Ryan is led to the house by Max's tracking of the twins' phone during a call. The twins continue to draw Ryan's attention by having him show up at a benefit event where the only survivor of the subway murders and new interest of Ryan, Lily Gray, is speaking. After an attempted attack, Ryan helps Lily go unharmed and shoots Luke in the arm, with the only other injury being to Lily's assistant, David. The twins escape as Luke tends to his injury.
Back at the hotel, along with Carlos and Gisele, Mark listen's as Carlos wants to meet Emma, who called Carlos's phone. Mark goes in his place and tells Emma about Joe's survival and his interest in Emma. He brings her back to his room where she meets Luke, Gisele and Carlos, though Luke soon-after stabs Carlos, killing him due to "no one liking him".
Mark later goes to Lily Gray, his mother's, home along with the rest of her "children". Mark gives Emma a phone when Joe calls and the duo meet Joe and Mandy in the woods. After taking Joe to his mother, Lily orders Mark to keep Emma busy so she can spend time with Joe. Mark does so and brings Emma to an art room so she can be free to do what she wants. Mark locks himself and Emma in Lily's art room to allow Emma to draw, an old passion of hers. Emma leans in to kiss him as he reveals he cannot handle body contact unless he initiates it himself and when he tells her she needs to learn about his disorder so they can "have a relationship", Emma angrily smothers her hands on his face causing Mark to fall over. She attempts to leave only to see that he locked the door. After Emma manage to leave, Mark wakes up and sees that she drew a picture of Joe, and not Mark, which leaves Mark upset.
He then wants to see his brother, only to see Luke with a dead Gisele and questions what happened. He brings Lily in and sees that Ryan killed her, to which the twins are more surprised to see that Lily is more concerned about Joe finding out about Ryan that Gisele's death.
After Luke is captured by Ryan, Lily and Mark to exchange him for an innocent bystander they kidnapped. Max and Mike give up Luke and Lily and Mark run for it. After hearing from Emma on the phone that Ryan killed Lily's remaining children (which is wrong as Joe really killed them), Mark tells Emma of the place they need to be to get out of the country, only for Emma to hang up the phone with the intent of betraying them. Mike finds them and starts shooting at them only for Luke to stop him and get shot twice by Mike. Just as Mark is about to go kill Mike, Lily frantically stops him, stating they need to go under the belief Luke died. Afterwards, Lily calls Joe about Luke's presumed death, only for Joe to express his contempt for Luke and Lily and how he's done with her, causing her to have an emotional breakdown with Mark comforting her.
Having lost his brother, Mark and Lily go on a rampage, swearing revenge on both Ryan, Joe and Mike for what happened. Mark and Lily start by abducting Max Hardy, Ryan's niece to a known serial killer. However, she was later saved. This was actually a diversion, as the duo later went to Mike's home and found his father, to which they forced him to watch via video as Mark kills Mike's father. As Weston runs out of the room crying hysterically, Lily teases Ryan that she has more surprises in store for him.
After a 3 episode absence, Mark is present as Lily hired several trained killers to bust his brother, who survived, out of custody, even if they have to kill several doctors, guards and even patients. Luke eventually does escape and has a tearful reunion with his brother and mother. Just as they are about to leave, Mark gets a phone call from non other than Mandy Lang, who asks if she can stay with him for now having left Joe's cult.
They take her to a remote home of Lily's, but when Mandy repeatedly refuses to give Joe's location, Mark and Luke proceed to torture Mandy. Joe and Emma discover that Mandy left Korban to find Lily, leading Joe to call Lily wanting Mandy. Lily says she'll let Mandy go if Joe gives himself up, but he denies the offer by telling Mandy he loves her and then hanging up the phone. Lily and the twins kill Mandy and eat dinner with her corpse at the table.
After finding Joe's location, Lily has her mercenaries corner Joe's Korban followers, which causes Mark to question his mother on why she needs to kill Joe and that they can escape the country now. Lily replies Joe must pay and tells Mark to man up and stop his whiny attitude. Lily has her men start by killing all of them except a small handful that escaped with Joe. When Luke goes to get a better look, Mark follows after him, unaware that their mother was moments later killed by Mike Weston.
Mark and Luke escape after hearing of their mother's death, swearing vengeance on Mike, Ryan and Joe. After Claire kills Emma during a vicious showdown, it entices Mark and Luke (who were likely intending on making an attempt on Emma's life themselves). She is then taken hostage by the twins as a leverage for luring Joe and Ryan and avenging their mothers execution while Mark is furious over Emma's death, showing he still held affections for her.
They force Ryan to take Joe to them and tie them and Claire up to a dinner table. They then threaten to kill Claire if they don't cooperate with their demands by playing "Russian Roulette". They force Joe to make a sincere apology over breaking their mother's heart and believing that Ryan killed their mother. After hearing that Ryan needs redemption over murdering his father's killer, Mark expresses his newfound admiration over Ryan, stating they'll now kill Max and Mike as penance, and just as they try to kill Claire, Mike and Max arrive and shoot Luke in his shoulder as they escape.
After everyone splits, Mike finds Mark and tells him that he killed Lily, not Ryan. Luke knocks Mike down but Max shoots Luke dead. Mark picks up Luke's body and runs off. He carries his dead brothers body to a remote location with him putting his dead brother's body in the car and drives off with Andrew Sharp in the car.
During a vicious assault in which he repeatedly stabs Mike, Mark is fatally gunned down and killed by a weakened Mike as he is about to attack Max, With his death the Gray Family is no more
Mark has more of a nicer and calmer personalty than Luke. He didn't have a lot of friends when he was young so he was an outcast while his brother was friendly and willing to make friends. Mark was very timid and quiet, as at times he does not fully support his brother's more insane ideas when dealing with others.
However, Mark can be just as ruthless as his brother, showing no remorse in killing people, especially those that wronged him, such as Mike Weston, having murdered his father and forced him to watch. After Lily was killed, Mark showed considerable more anger than he had previously shown as well as being distraught, not even pretending that the woman he and Luke had killed was still alive.
Mark is very close to his brother Luke, as the two reciprocate each other's brotherly love for one another, especially after their reunion from his capture. in season 3 Mark now suffers from a severe personality disorder, and his deceased twin brother is his other half. This has caused him to argue with himself and become much more unstable, as he has talked to himself in public as Luke, as well as switching personalities at any time.
- The Subway massacre: Five unnamed victims (stabbed along with Luke and Carlos Perez)
- The Fisher house killlings:
- Richard Weston (neck slashed)
- Mandy Lang (killed along with his brother Luke)
- Trisha Brumell (killed along with his brother Luke)
- Claire Matthews (abducted; was rescued)
- Unnamed woman (shot once in the chest)
- Kyle Locke (non-fatally slashed in the arm)
- Unnamed journalist (stabbed in the chin)
- Three unnamed firefighters (one he killed in bed, one stabbed in the back and one struck in the back with an axe)
- Juliana Barnes (ironed her to death)
- Ryan Hardy (attempted; shot at with a rifle, but missed)
- Mike Weston (attempted; shot at multiple times with a rilfe, but missed)
- 2 unnamed assassins (shot to death)
- Unnamed stage owner (stabbed to death)
- Mike Weston (attempted; stabbed 4 times in the back, unknown if he died)
- Max Hardy (attempted to stab; was killed by a weakened Mike)
- Mark has Haphephobia, a fear of being touched.
- In Freedom, it's revealed Mark is the younger twin brother.