Plot
During a power outage in the New York City skyscraper where he works, corporate suit David Stillwell decides to exit using the darkened stairs. While descending, he encounters an attractive young woman who seems to know him, but he has no recollection of her. Alarmed, she flees to the sub-basement.
Outside is the body of the noted philanthropist and leading world peace activist, Charles Calvin, who apparently jumped from his 27th floor office. At a nearby bar, Stillwell feels ill-at-ease and flashes back to his encounter with the woman. He returns to look for her, but now there is no sub-basement. A large pugnacious man, Willard, is working in the machine room and orders Stillwell to leave.
At Stillwell's apartment building, a stranger, Lester, pulls a gun and forces him into the apartment. He demands Stillwell get his briefcase and go meet "the Major". Stillwell, not knowing what he is referring to, knocks out Lester and hides him in a hallway service closet. Stillwell then checks his briefcase and finds it completely empty.
While attempting to report the encounter to the police, Stillwell becomes distressed by basic questions about his background and storms out. He suddenly realizes he has no memory of anything before the two years of his present job. He consults a psychiatrist, Dr. Broden, who throws him out, declaring it impossible to have amnesia for two years without being aware.
Stillwell hires novice private detective, Ted Caselle. Skeptical at first, Caselle begins to believe his story after spotting Willard following them. He inspects Stillwell's apartment. The refrigerator, which was previously empty, is inexplicably fully stocked, and his briefcase is now full of files. Stillwell takes Caselle to his office, located near Calvin's, but there is now only a blank wall. They go to the basement; Willard arrives and shoots at them, but they escape.
Stillwell encounters the woman again, who says "the Major" urgently wants something from him. She reveals her name is Shela, and that she and Stillwell previously had a relationship. She reluctantly accompanies him to see Joe Turtle, a concierge at Stillwell's building who knows him, but Turtle has been beaten to death by Lester. Stillwell forces Shela to see what her associates are capable of.
The two spend the night together, but Stillwell wakes to find Shela gone. Lester and Willard are waiting downstairs. He disarms Lester and uses him as a shield, but Willard callously kills Lester. Stillwell escapes and goes to Caselle's office, but finds him dead.
Stillwell's intermittent flashbacks are becoming more regular and detailed. He revisits Dr. Broden. They work out that Stillwell's amnesia is only two days old, and that false memories have displaced recent traumatic ones. Stillwell realizes he is not a cost accountant, but a "physio-chemist" and Calvin's protégé. His home is New York, but he's spent the last two years in California working at a private research facility in a sub-basement lab under a man named Sylvester Josephson.
Stillwell visits Calvin's widow, who believes he killed Calvin and empathizes with him for doing so. Stillwell suddenly remembers Calvin falling through a window. He notices a photograph of Calvin with an Army officer that Mrs. Calvin says is Major Crawford Gilcuddy. Stillwell goes to see the Major, where he also finds Josephson, Willard (who beats him brutally), and Shela (who is the Major's girlfriend).
More memories begin to return. Stillwell had discovered a method to neutralize nuclear radiation, making fallout less deadly. He then went to New York to reveal the breakthrough to Calvin. There he discovered that despite Calvin's posturing as a peace advocate he was illegally conducting business with the Major, who sought to hijack Stillwell's work – which actually made using nuclear weapons more attractive, and more profitable, as they could be used and consumed like conventional weapons. While arguing with Calvin, Stillwell had raged over becoming a mere "cost accountant" for nuclear war. To prevent his peaceful discovery being misused, Stillwell attempted to burn the document containing the formula; as Calvin lunged at it he'd tripped out the window to his death. The combined shock caused Stillwell's amnesia.
To force Stillwell to recreate his formula, the Major has Willard point his gun at Stillwell's head and play Russian roulette. With each click of its trigger both memories and anger swell in him. Shela shoots Willard. Josephson grabs her gun, but Stillwell convinces him the Major will not let Josephson live (as he knows too much about the secret doings); Josephson calls the police. Stillwell and Shela embrace.
