In England, an affluent, elderly man suddenly bursts into flames while walking from his front porch to his car. Despite the efforts of those at the scene to extinguish the fire, the man is burned alive.
     Mulder and Scully are approached by Phoebe Greene, Mulder's ex-classmate and former lover, who is employed as an inspector by Scotland Yard. Greene tells the detectives about the death of the man in England, and how it is but one of a series of similar murders aimed at the British aristocracy. Sir Marsden, who narrowly escaped being burned alive in a similar incident, has temporarily relocated his family to Cape Cod. Mulder and Scully agree to aid Greene with the case. Scully, however, is hard pressed to contain her obvious jealousy.
     Special Agent Melvin Beatty, an arson specialist, examines the evidence linking the fires, but is at a loss as to how the blazes were started. Mulder's notion that it may be attributed to pyrokinetics-an individual's ability to conduct and control a fire-is scoffed at by Beatty.
     Mulder confesses to Scully that he is terrified by fire, and admits that Phoebe is all too aware of his phobia. He tells Scully he will handle the investigation without her help.
     Unbeknownst to Sir Marsden and his family, the caretaker at their Cape Cod home is the same man who gardened for the elderly man who was set ablaze in England. That man, who call himself Bob, walks to a local bar and sets it ablaze using his pyrokinetic power.
     Mulder and Greene interview a survivor of the blaze. The are intrigued when the survivor tells them that a British man started the blaze by causing himself to ignite.
     Mulder and Greene stake out an elegant party attended by the Marsdens hoping to trap the arsonist. After surveying the hotel where the party is given, Mulder and Greene conclude the arsonist will not strike. They take advantage of their surroundings for some intimate slow dancing on the ballroom floor. Scully arrives at the party with information regarding the case. She notices that the hotel security status grid is lit up, indicating a fire somewhere on the upper level. She interrupts Mulder and Greene with the news, shattering an intimate moment. Mulder races upstairs but is overcome with smoke. Bob races out of the hotel with the Marsden's children and is hailed a hero.
     Scully takes advantage of Mulder's hospital stay to fill him in on her research. She believes the arsonist uses a highly flammable accelerant, such as rocket propellant, to fuel the fires. Scully also suspects she may have pinpointed the arsonist, a man named Cecil L'Ively, who acted as caretaker for two of the victims. They come to realize that the Marsden's caretaker is the same man.
     The detectives rush to the house in Cape Cod and evacuate the family. Mulder catches Greene sharing a passionate kiss with Sir Marsden, ending his interest in her. Mulder and Scully encounter Bob/Cecil, who has rigged the entire dwelling to catch fire. Mulder becomes paralyzed with fear when he encounters the fire. Phoebe splashes accelerant on Bob and he bursts into flames. Mulder and the others escape from the house and watch as it is consumed in fire.
     Bob's flesh regenerates itself, however, and he soon recovers inside his heavily guarded cell.