Donnie Pfaster loses his job at a funeral home after his boss discovered him cutting hair from the corpse of a pretty girl. Not long after Donnie's dismissal, Special FBI Agent Moe Bocks receives a call regarding the mutilation of buried corpses at a graveyard in Minneapolis, Minnesota. Suspecting the incident might be related to UFOs, Bocks notifies Mulder and Scully, hoping their expertise might help shed some light on the bizarre incident. Mulder, however, recognizes signs of an escalating death fetishist. Despite her years of work performing autopsies, Scully is nonetheless severly disturbed by the manner in which the bodies are mutilated. Hair has been snipped away in clumps, and fingernails have been torn out with pliers. Scully is plagued by nightmares featuring a demon. In the dreams, she becomes one of the killer's victims.

When more mutilated bodies turn up, Mulder fears the fetishist's compulsion might lead to murder. His suspicions prove correct: Donnie employs the services of a prostitute, then murders and mutilates her. After examining how the body was defiled, Mulder suspects the killer has a deep hatred toward women.

Donnie makes an effort to blend into the community. He takes a job as a delivery man, and while working his route he wins the confidence of Ellen Brumfield and her family. He enrolls in a mythology class at a junior college, but his attention is drawn to a pretty coed who sits at the front of the class. One night in the school's parking lot Donnie pins the girl to her car. She strikes back by kneeing him in the groin, and Donnie is arrested. That same night, however, a different suspect with a history of assault is also arrested. Mulder and Scully interview the man at the jail but determine he is not a suspect. In a nearby cell, Donnie takes note of Scully's name.

Bothered by her reaction to the case, Scully flies back to Washington and seeks the services of Karen Kosseff, a member of the FBI's Employee Assistance Program. Scully admits her recent abduction and the elements of the case combined to affect her judgement. Meanwhile, forensics lifts a fingerprint off the prostitute's corpse. Mulder and Bocks trace the print to Donnie, leading them to his apartment. They search the dwelling and discover a human finger inside a freezer.

Donnie begins stalking Scully after she flies back to Minneapolis. He forces her rental car off the road and kidnaps her. Police locate the car. Mulder and Bocks search for clues but come up empty-handed. Mulder realizes that Donnie's psychological profile sketches the mind of a deviant who, like notorious murders before him, is the embodiment of evil.

Scully breaks free from her bonds and attempts to elude her captor. Donnie gives chase, gun in hand. The two grapple for the weapon, and as Scully looks at Donnie's face, she sees the visage of a demon, the same horrible creature from her dream. Mulder and Bocks storm Donnie's hideout. Donnie drops his weapon and is taken into custody.