Plot Summary:The FBI arrests a serial killer John Mostow, responsible for the killing of at least 7 men. Mostow claims he was possessed by an evil spirit, a fairly common claim among serial killers as Scully points out. With Mostow in custody however, other very similar attacks occur leading Mulder to think Mostow may be telling the truth. The agent in charge of the case, the renowned Bill Patterson, doesn't think much of Mulder or the kind of cases he deals in. As the killings continue however, the evidence not only points to Mulder's theory being correct but points to the killer.