Booth and Brennan investigate the remains of a man found in a church with horns and a vestigial tail, resembling a demon. The case leads them to Havenhurst Sanitarium, where the victim was committed, as he had schizophrenia. The case causes intern Arastoo Vaziri to talk about his beliefs of good and evil, including revealing a secret from his past about serving in Iraq where he was forced to kill someone.