FBI Specialist Debra Parker was an FBI agent working with Ryan Hardy.
Debra was raised in a cult, Serenity Hill, located in Church Rock, Iowa. In 1989, still a child at the age of 14, she was raped by the leader of the cult, Dale, as an offering. After she realized she was going to be raped she tried to leave, but her parents made her stay, allowing the rape to happen. After she was raped, she escaped. In 2004, 15 years later, she visited her parents and told them that she had forgiven them. To her disappointment, her parents, brainwashed by the cult-leader, saw Debra's escape as blasphemous and refused to forgive her actions. They also thought they were being punished for her escape from the cult. However, Debra came to say she loves them and always will, and that she forgives them, which seems to have left them speechless. She leaves disappointed later.
As an adult, Debra specializes in cults and fringe religions.
Debra Parker is in charge of the Case against Joe Carroll's cult and works with Ryan Hardy. She serves as an information over Joe's cult and his motives, being a partner alongside Mike Weston.
in The Siege, Debra tries to talk to Emma about killing her mother and her artwork, knowing she has potential, but Emma refuses to listen knowing she's trying to reason with her. Despite their efforts, they are outsmarted after discovering Joe's followers in the police and SWAT that help them all escape.
Following Claire's abduction, Debra visits a depressed Ryan and encourages him to get out of bed and back to work that he can't just give up less everything would be for nothing. He eventually does so and gain a lead to a former militia bunker to follow Vincent, but he escapes. They find numerous records, armory and weapons, leading them to suspect it's a boot camp of sorts. While in the bunker, they find followers in training that escaped and Debra fights off one of them and is saved at the last second by Ryan. She later thanks him for that and Ryan says he thanks her for bringing him back to work.
In The Curse, she assists in tracking down Daniel Monroe till Jacob holds her hostage for Joe's release. Ryan lets them go and saves her and Mike. Once Mike recognizes Roderick from the station, Debra assists in tracking his location. After Joey is rescued, a follower named Melissa shows up intent on Ryan's previous offer of turning herself in, but as they prepare to bring her to the back, she reveals her true nature and stabs Nick Donovan in his eye as Mike and Ryan kill her as a terrified Debra tries to help him.
In "The End is Near", she assists Hardy, Weston and the rest of the FBI at searching the evacuation center for followers. After the chaos starts, she follows Alex down a hallway. After shooting a female follower, Parker meets another FBI agent. As the 2 search a room, Parker is grabbed from behind, and Alex comes up and holds a knife to her. The 2 men bring her to a small, empty coffin in the woods. Ignoring Parker's protests, they seal it shut, burying her alive.
In The Final Chapter, a phone inside the coffin in which she was trapped let her get a call from the FBI, trying to localize and save her. Debra seems to accept her fate, telling Ryan that her only regret is "my family" and her inability to make amends with them. She asks Ryan to tell them she loves them. Ryan and Mike finally find her, lifeless inside the coffin. Ryan desperately tries to resuscitate her, but is unsuccessful.
Though Debra is dead, her character continues to have an impact on both Ryan and Mike, which resolves them both to return to the FBI to take down Joe Carroll after hearing of his revival to the world. At the same time it caused Ryan to become more distant towards others, lest they share the same fate as she did.
In "Unmasked", it's revealed that the reason Joe was successful in faking his death was because former FBI agent Jana Murphy hacked Debra's email various times by using Gina Mendez's security clearance codes so to make sure she wouldn't be caught. Once Mike and Ryan discovered this, they were able to track Jana down as she killed herself, effectively costing Joe his mole in the FBI.
- 2 unnamed Followers (The End is Near)
- Debra Parker replaced Jennifer Mason as a main character.
- She carries a Glock 19 or 23 as her FBI issued sidearm.
- She gave a book of Edgar Allan Poe's writings to Joe Carroll while he was in prison. This caused much speculation among viewers as to whether or not she was part of Carroll's cult. (Chapter Two).
- Debra named Joe Carroll's cult religion as "Carrollism", stating they have to call it something.
- She has a younger sister, Beth, who apparently is not a member of the cult their parents belong to. ("The Final Chapter")
- The character of Debra Parker was widely praised by both viewers and critics alike with the latter complimenting actress Annie Parisse's performance and the development of the character. The writing off of her character in the finale of the first season sparked outrage among critics (as well as viewers), who deemed her death as a "mistake" in terms of plot. In truth, many of them were hoping she'd be revealed as a follower--which was anticipated throughout the first season as a result of her meeting with Joe Carroll.