S1E23 · Roland

At a physics research lab, intellectually disabled janitor Roland Fuller is scolded by scientist Dr. Keats for forgetting how to use the facility's keycard locks. Keats walks in on his colleagues, Frank Nollette and Ronald Surnow, arguing over a prototype jet engine. After Keats and Nollette leave, Surnow enters the facility's wind tunnel to make adjustments. However, Roland activates the tunnel's turbines, killing Surnow. Roland examines the scientists' whiteboard and changes some of its equations.

Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) investigate Surnow's death. Scully learns another member of the research team, Arthur Grable, had died several months earlier, and suspects industrial espionage. Mulder examines the handwriting on the whiteboard and concludes it was written by at least four different people, suggesting a fourth individual was present. Keats and Nollette both inform the agents that Roland was the only one left in the facility at the time of Surnow's death, but do not believe him capable of murder.

Nevertheless, Mulder and Scully visit Roland at his care home, where he denies seeing anything unusual. He displays his mathematical prowess by rapidly counting the star designs on Scully's blouse; however, his handwriting does not match the fourth sample from the whiteboard. The discussion ends when Roland experiences a violent vision involving Keats' head being frozen and has what seems to be a fit. Later, he has another vision of someone killing Keats. Roland appears at the lab and submerges Keats' head in a tank of liquid nitrogen, shattering it before typing at a computer. The next day, the agents notice the computer was used hours after Keats' death and realize that the number Roland had written on an art project previously is the password to files containing the work of Grable, which have been worked on since his death.

Investigating Grable's death, the agents learn he had hired Roland. They suspect Grable faked his death and is killing his colleagues, using Roland as a patsy. Grable's body was never brought to the morgue, nor was a funeral held. However, Nollette brings the agents to a cryogenic facility where Grable's remains are being stored. A photo of Grable reveals he is Roland's identical twin. Mulder becomes convinced that Roland is being periodically controlled by Grable.

Nollette sneaks into the cryogenic facility and sabotages Grable's unit, thawing his remains. Roland returns to the lab and is in the process of pushing the prototype engine to mach 15 when Nollette enters. Nollette admits to stealing Grable's work and prepares to shoot Roland; when he is distracted, Roland strikes him and drags him into the wind tunnel. The agents arrive in time to convince Roland not to kill Nollette. At the same time, the rising temperatures in the cryogenic unit kill Grable. Roland is taken from his care home to a psychiatric institute for testing. As he leaves, he combs his hair in the style of his brother, suggesting he is not free of Grable's control.