A man disappears from a locked hotel room, and the only clue left behind is a strange black impression scorched onto the floor. When two other victims meet the same fate, FBI Agent Fox Mulder believes the deaths may be due to spontaneous human combustion. Until Mulder and his partner Agent Dana Scully trace the deaths to a company called Polarity Magnetics, where scientists are working on the creation of "dark matter" -- reducing matter to pure energy. There Mulder and Scully track down a man who is literally afraid of his own shadow -- and the agents discover that his shadow may actually be the killer.