Scully becomes very worried about Mulder when he begins acting very, very strangely and seems to lose his memory while investigating a case. This leads him to be the main suspect in a series of brutal murders.

Mulder has a strange vision where he sees his mother and father looking horrified at something that has entered their home. He then suddenly awakens with blood all over his shirt and fingers in a motel room. When Scully arrives at Mulder's wish, he cannot remember how he got to the motel and Scully discovers that two rounds had been fired from Mulder's gun.

Scully manages to trace a car that is parked outside Mulder's motel room to David and Amy Cassandra so the agents travel to their residence and discover a home with dozens of paintings of a clapboard house on the walls. Mulder realizes that he was actually in the home but as he is suffering from a mental blackout, he cannot remember why. The housekeeper at the Cassandra's home manages to tell the agents where the house in the painting is located but when Mulder approaches the house with Scully he suddenly goes into a seizure and in flashback sees a young Cancer Man inside the house of his parents. When the seizure ends, they walk into the house where they discover the dead bodies of Amy and David.

After analysing the blood on the Cassandra's and Mulder they are found to be an exact match so Detective Curtis places Mulder under arrest. Scully though finds traces of a drug called Ketamine in Amy's and Mulder's blood which could be the reason for his bizarre memory loss. Meanwhile, Michael Fazekas, an admitting officer steps inside the police station's bathroom and suddenly shoots himself in the head for no reason. Scully looks over the dead body of Fazekas and finds a scab similar to one found on Amy. The Detective later reveals that Fazekas was a UFO fanatic and when Scully searches his appartment she finds a UFO magazine with a picture of Amy who believed she was an abductee.

Further forensics investigation reveals that the blood on Mulder's shirt does not correspond to Amy's and that the Cassandras died as the result of a murder-suicide. Scully also finds that Amy was dating a psychiatrist, Dr. Charles Goldstein and that he was experimenting on using therapy to stimulate electrical impulses in the brain.

Later, Mulder suffers another bizarre seizure and this time sees the vision again of a young Cancer Man but this time he pulls Mulder's mother towards him as if to kiss her. Mulder is angry with his mother for betraying him and his father after this so he drives with Scully to his mother's home to confront her accusing her of lying that she had to be forced to choose between Samantha and him. She denies the accusations so Mulder storms off. Mrs. Mulder explains to Scully that Mulder suffered from epilepsy until he was 12 years of age.

Mulder drives to meet with Dr. Goldstein where he pulls a gun on him and forces him to stop his treatment so that he can relive his past. The doctor instead drugs Mulder and lowers a spinning needle to Mulder's hairline (where the identical scabs were on Amy and Fazekas). The police arrive to arrest the doctor but Mulder is nowhere to be found. Goldstein tells Scully that Mulder left to "exorcise his demons". She manages to locate Mulder but he is on the floor pointing his gun at Scully having a seizure. Scully explains to Mulder that the hallucinogen that was injected into Mulder's body has affected his mind and his visions and that the memories he has been reliving are not to be trusted. Mulder fires his gun but it misses Scully and hits the mirror behind her shattering it. Mulder puts down his gun and breaks down in tears into Scully's arms.....