S2E23 · Soft Light

At a hotel in Richmond, Virginia, Chester Ray Banton (Tony Shalhoub) reaches a room and frantically knocks on the door while shouting the name ″Morris″. Banton's shouts attract the attention of Patrick Newirth, a guest in the room across the hall. When Newirth looks through his door's peephole, Banton steps back, causing his shadow to slip beneath Newirth's door. Newirth suddenly evaporates, leaving a strange burn mark on the floor. Banton realizes what has happened and flees the scene.

The case of Newirth's death, the latest in several of its kind, is assigned to local detective Kelly Ryan (Kate Twa). She seeks help from Dana Scully (Gillian Anderson), her former instructor at the FBI Academy. Fox Mulder (David Duchovny) also takes part in the investigation, believing Newirth died from spontaneous human combustion. While searching the home of an earlier victim, the agents realize that both she and Newirth had recently traveled by train. Meanwhile, Banton sits in a train station, cautiously looking at the floor; because the room is lit by soft light, his shadow cannot be seen. After he leaves, Banton is confronted by two policemen patrolling the area. Despite Banton's warnings, the officers step into his shadow and disappear, leaving more burn marks.

The following day, while reviewing the station's surveillance tapes, Mulder sees footage of Banton staring at the floor. After blowing up the frame, Mulder sees the logo for a company called Polarity Magnetics on Banton's jacket. At Polarity Magnetics, the agents meet scientist Christopher Davey (Kevin McNulty), who identifies Banton, a physicist conducting research into dark matter. Davey reveals that Banton disappeared five weeks earlier after an incident in his laboratory in which he was locked in a target room with an active particle accelerator and exposed to a large amount of subatomic particles. His account is enough for Scully to consider spontaneous human combustion, but Mulder is now doubtful of this theory.

The agents find Banton at the train station, but he runs to a poorly lit area. He indicates that walking into his shadow will kill the agents, so Mulder shoots out the overhead lights. Banton allows himself to be taken to a mental hospital, where he is put in a room with soft light per his own request. He tells the agents that the accident in his lab caused his shadow to behave like a black hole, splitting atoms into component particles and reducing matter into pure energy. Banton claims that the deaths were all accidents, and that the government wants to exploit him.

Ryan and her superior stop the questioning and declare the case closed, despite Mulder's objections. Mulder contacts X (Steven Williams), who assures him that the government has no interest in Banton. However, X and two associates later attempt to remove Banton from the hospital by cutting the power. In the process, X's associates are killed when the emergency lights turn on and Banton's shadow falls upon them. Banton flees from the hospital.

Banton returns to Polarity Magnetics and is confronted by Ryan, whom he reluctantly kills with his shadow when she tries to arrest him. Banton orders Davey to destroy him with the particle accelerator, but Davey reveals that he has been helping the government hunt him down. Davey locks Banton in with the particle accelerator, but is shot by X. Mulder and Scully arrive soon after, seemingly too late to save Banton from being vaporized by the accelerator; Mulder realizes that X has betrayed him, and tells X to never contact him again. The case is considered closed, but Mulder notes that Davey disappeared after the incidents. At a research facility, X watches as experiments are being performed on a despairing Banton.