Jason Nichols and Lucas Menand, researchers at the Massachusetts Institute of Technology, become embroiled in an argument as they walk down a city street. They are approached by an elderly man, who warns Menand that he will be run over by a bus at exactly eleven forty-six that evening. Menand tells a campus security cop that the old man is harassing him. The guard places him in the back seat of a sedan and drives away. A few moments later, Menand is run down by the bus... at exactly eleven forty-six.

     Mulder and Scully review the facts of the case. Nichols was taken into custody after the bus driver told police that he pushed Menand into the path of his vehicle. But Nichols tells authorities he was attempting to save Menand-as an unidentified old man had forewarned of his colleague's impending death.

     The security guard who arrested the old man is found frozen to death. Scully concludes guard was somehow exposed to some sort of chemical refrigerant, as weather conditions are too warm to explain the corpse's frigid internal temperature. Mulder interviews Nichols at the police station. Nichols explains that he and Menand had been arguing because Menand threatened to go public with a claim that he had falsified data on a research paper.

     A short time later, the elderly man kills Dr. Yonechi, a Japanese researcher, by pricking him with a metallic stylus. Mulder and Scully examine Yonechi's frozen corpse. Lab tests reveal that the doctor was injected with an unidentifiable chemical compound. The agents approach Nichol's girlfriend, Lisa Ianelli, who is also a researcher. She recognizes the chemical compound as a rapid freezing agent that Nichols had been engineering for years. But she points out that the chemical has not yet been invented. Lisa tells the agents that if Yonechi was injected with the chemical, he may not be dead. With Lisa's help, Scully and a team of medical personnel successfully resuscitate Yonechi. But his body temperature suddenly and rapidly begins to increase, until finally, he bursts into flames. Lisa realizes she made an error when she recommended that doctors remove Yonechi's body from a tub filled with yellowish fluid.

     Lisa confesses that it was she who falsified the data to get the research grant (Nichols is in jail because he is covering for her). Those who would have figured out the truth-Menand and Yonechi-are now dead. Police receive a tip that the elderly man is living at a nearby hotel. Inside the elderly man's room, the agents discover a faded color photograph picturing Nichols, Yonechi and Lisa toasting champagne glasses inside the cryology lab. Mulder realizes the photo was taken five years in the future-on the day the researchers successfully synthesized the freezing compound. The elderly man is attempting to alter that future: when he failed to save Menand from being killed by the bus, he killed Yonechi. Mulder also realizes the elderly man is none other than Jason Nichols.