The exploits of FBI Special Agents Fox Mulder and Dana Scully who investigate X-Files: marginalized, unsolved cases involving paranormal phenomena. Mulder believes in the existence of aliens and the paranormal while Scully, a skeptic, is assigned to make scientific analyses of Mulder's discoveries that debunk Mulder's work and thus return him to mainstream cases.
A case involving a strange old man warning two scientists of events in the immediate future which come to pass (and the use of their experimental flash-freezing compound that does not exist yet) has Mulder believing that one of the scientists has come from the future to stop his own scientific breakthrough from becoming reality.