Forensic psychologist Kristen Bouchard is hired by the Catholic Church to determine whether a serial killer is possessed by a demon or merely a psychopath.

Kristen, David and Ben investigate a supposed miracle when a teenage girl comes back to life after being declared dead for almost three hours; Kristen meets with her former boss and runs into Leland Townsend.

After a high-strung theater producer's behavior turns from demanding to what is believed to be demonic, Kristen, David and Ben must assess the situation. Kristen discredits her nemesis, Leland Townsend, before he can ruin a 17-year-old boy's life.

Leland assists convicted serial killer Orson Leroux with having his conviction overturned; Kristen is called into court to testify while her daughter, Laura, undergoes emergency heart surgery; David witnesses a woman's evil instincts firsthand.

The team receives disappointing news. Kristen meets mysterious stranger Ellie, who claims to be an old friend of Sheryl's. A game between the two reveals disturbing information about Kristen's future...and about Ellie herself.

Sister Andrea gives the team their last assessment, a man who believes his doppelganger has possessed him and has a personal connection to the nun.