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.

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.

Kristen, Ben and David are hired to evaluate Eric, a seemingly psychopathic 9-year-old boy; Eric takes a liking to David, which leaves them hopeful they can curb his violent behavior; Kristen's daughters lie about a game their grandmother bought.

On Halloween night, Kristen and David are sent to assess an exorcism; Ben goes on his favorite show, where he debunks supernatural finds with fellow unbeliever Vanessa.

When the Catholic Church asks Kristen, David and Ben to assess the veracity of a local prophetess, Grace Ling, they are shaken when they see one of her visions come to life.

When Bridget confesses to murder during her exorcism, Monsignor Korecki asks Kristen, David and Ben to investigate if the details match any open cases and if the woman really is possessed by a demon.

When David recognizes one of the sigils in the Poveglia Codex from his father Leon's artwork, he and Kristen journey to a remote art commune to investigate its meaning and how it's related to David's family.

David is shocked to learn he is being sued for inflicting severe psychological harm on Caroline Hopkins, after he assisted in her exorcism. The accusation leads him to question his future as a priest, especially once he develops a very close connection with his defense attorney, Renée Harris.

Kristen, David and Ben are called to investigate an insidiously addictive Christmas song that's spreading among an increasing number of students, and the dangerous relationship between online influencers and their impressionable young followers.

After David is badly wounded, he is determined to fight off the menacing presence of death from his hospital bed.

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.

David, Kristen and Ben assess whether a pregnant woman is possessed when she claims one of the twins she’s carrying is evil. Their investigation leads to a fertility clinic where they discover a connection to all of their encounters throughout the season. Also, Kristen questions one of her daughters’ capacity for evil upon realizing that she also used that fertility clinic.