Marty is part of The Seven, a group of Revenants who make it a sport to kill the heir. This means Marty was present the night of Ward Earp's death. Marty is first seen in The Big City where a time capsule of Shirley Dixon is being dug up after a hundred years. Marty and his posse, consisting of Samuel Larson and Gary Smith, kill the Deputy Mayor in order to get Dixon's diary (the voice of a mute). With the left hand of a innocent murderer already in their possession, the last piece they need to leave the Ghost River Triangle is the locket of Stanley Gatewood's wife (a loveless heart). At some point, probably when he was human, Marty worked for Stanley Gatewood, who managed the bank where the locket is stored, so it was his responsibility to acquire it for the spell. Marty ends up murdering a worker at the graveyard and digs up Stanley's grave while looking for the combination to the safe. He is interrupted by Wynonna Earp and is chased away. Wynonna and Xavier Dolls arrive at Crown Surplus just as Marty's group starts taking hostages. They release three of the hostage, but keep Champ Hardy and Shorty, in return for Wynonna's help in opening the safe. Marty ends up stabbing and temporarily killing Gary when he gets frustrated about not being able to open the safe. After it's opened, Sam, Marty, and their three hostages flee the surplus store to a farm near the edge of the Ghost River Triangle. Sam shoots Marty when he gets upset that his host body, Shorty, is injured. Once Wynonna is reunited with Peacemaker, she shoots Marty and sends him back to hell.
Despite working together for many years, the three of them aren't particularly close to each other. Sam doesn't seem upset when Marty temporarily kills Gary and later Sam shoots Marty when they fight over Champ's body.
Dolls suspects that they channel the powers of a hellhound
- Super strength
- Increased speed
- Finely tuned sense of smell
- Marty has been sent to hell three times, which as caused him too