The episode opens in a hospital emergency room where a teenage girl, Keira Grayson, is found beaten to death. From security footage, Green and Briscoe identify Bill Crawford, who brought Keira to hospital. They also find that the day before Keira's death, her mother had been in contact with Crawford. Mrs. Grayson has an alibi, since she was at a Catholic church at the time Keira died. The detectives discover that through the church, Mrs. Grayson and Crawford both know a former nun named Sister Rosa Halasy. The detectives find evidence of Keira having been restrained and beaten in Sister Rosa's apartment, so Sister Rosa is arrested.
Crawford confesses that Keira died during an exorcism intended to cure her severe behavioral problems. Because of Mrs. Grayson's obviously fragile mental state, which would earn a jury's sympathy, McCoy allows her a plea deal. Crawford also gets lesser charges, and Sister Rosa is the sole defendant to murder. But in court, Sister Rosa testifies that she hears messages from St Michael, who directs her to do God's will. She says that during the exorcism, St Michael told her to send Mrs. Grayson away and then crush Keira's chest with a crucifix to drive the devil out. McCoy fears losing the case if he tries to challenge Sister Rosa's religious convictions.
When cross-examined by McCoy, Sister Rosa says that God will hold her responsible for not being able to defeat Satan and save Keira; but that no crime was committed. She denies wanting to hurt Keira and says that she understands what this looks like to outsiders. McCoy convinces the jury that, even if Sister Rosa really is a messenger of God, she is still human and must abide by the same laws and moral principles as anyone else. They convict, and while Carmichael is satisfied that justice has been served, McCoy still feels conflicted.
This episode contains examples of:
- Abusive Parents: Mrs. Grayson kept Keira chained to a radiator in their apartment.
- Crazy Homeless People: Bill Crawford is homeless and has an obvious mental disability.
- Death of a Child: The episode starts with Keira's death.
- Domestic Abuse: Trying to narrow down which of two missing girls the victim could be, Briscoe and Curtis apprehend a man with a history of violently abusing his wife, who they believe could have murdered his daughter (although it's soon discovered he did not.)
- Hollywood Exorcism: Lampshaded when Carmichael talks to the head of the diocese that Sister Rosa's former convent belongs to. He says that exorcisms are nowhere near as dramatic as they are in the movies and are rarely performed.
- Insistent Terminology: Rosa Halasy is no longer a nun but still known to everyone in the community as "Sister Rosa."
- Maybe Magic, Maybe Mundane: It's left for the viewer to decide whether Sister Rosa really does have a religious "gift", especially after a defence witness testifies of a successful exorcism that she performed on his son.
- Nun Too Holy: The Mother Superior of Sister Rosa's former convent implies she was this, due to how extreme her beliefs could be.
- Outliving One's Offspring: Keira's mother survives the episode.
- Ripped from the Headlines: Based on the cases of Terrance Cottrell and Charity Miranda, both children who died during exorcisms gone wrong.
- Troubling Unchildlike Behavior: Keira engaged in plenty of this, including seriously injuring other kids.
