|Significant Other(s):||unnamed woman† (wife)|
|Portrayed by:||Henry Ian Cusick|
|First appearance:||Eye for an Eye|
|Latest appearance:||Daddy Issue|
Dr. Trent Marsh was a psychiatrist and strongly presumed serial killer who appeared in season 3. He was played by Henry Ian Cusick.
In 2003, Trent's wife, was murdered in a home invasion. The prime suspect was a sex offender named Nathan Jarvis, who escaped conviction due to a lack of evidence. A year later, Trent went back to school, got a PhD in clinical psychology and became a grief therapist. Over the years, he treated several people, among them Paul Winters and Susan Hart, both of whom had had loved ones who were murdered and whose killers escaped. In 2012, he apparently began a plan to avenge their murders as well as his wife's death. That was the year Nathan Jarvis disappeared without a trace. In 2013, during "Eye for an Eye", Freddie Delgado, who had shot and killed Paul Winter's young daughter and escaped justice, was shot to death in a garage. Later in the episode, Laurie Kaiser, who had thrown acid in the face of her boyfriend and killed him after he married another woman, Susan Hart, turned up dead as well. When Megan and her unit find that Trent is the strongest connection between them, she figures that he killed for them. When brought in for questioning, he denies killing anyone. Unfortunately, the DNA evidence left at both scenes doesn't belong to him, but Nathan Jarvis. Megan figures that Trent made him disappear, committed the two murders and planted his DNA at the crime scene to frame him, but since they cannot prove the theory or that Trent was in any, Trent walks.
Trent returns in "Daddy Issues", when he runs into Megan on the street by accident. He starts talking to her about her father's suicide. He later approaches her deliberately in the garage and implicitly offers to help her get payback on her father's murderer. She turns him down. When she is kidnapped by Chief Angela Martin, who is revealed to be her father's murderer, and is about to be killed, Trent surprises her and saves Megan's life by sneaking up behind them and shooting Chief Martin in the back before slipping away. When Tommy and the police arrive at the scene, Megan tells Tommy that Trent was the shooter. When they raid his office, he is gone, having disappeared.
During his known murders in "Eye for an Eye", Trent killed his victims the same way they killed their suspected victims.
- 2012: Nathan Jarvis (presumably; had killed his wife)
- Freddie Delgado (shot in the head; had killed a young girl)
- Laurie Kaiser (threw acid in her face; had killed her ex-boyfriend)
- Chief Angela Martin (shot in the back)