The film begins with what a BBC reviewer called 'perhaps one of cinema's most innovative opening sequences.' The scene is a long, behind-the-back tracking sequence featuring Frank Bigelow (Edmond O'Brien) walking through the hallway of a police station to report his own murder. Oddly, the police almost seem to have been expecting him and already know who he is. A flashback begins with Bigelow in his hometown of Banning, California where he is an accountant and notary public. He decides to take a one-week vacation in San Francisco, but this does not sit well with Paula Gibson (Pamela Britton), his confidential secretary and girlfriend, as he does not want her to accompany him.

Bigelow accompanies a group from a sales convention on a night on the town. At a 'jive' nightclub called 'The Fisherman', unnoticed by Bigelow, a stranger swaps his drink for another. The nightclub scene includes one of the earliest depictions of the Beat subculture. The next morning, Bigelow feels ill. He visits a doctor, where tests reveal he swallowed a 'luminous toxin' for which there is no antidote. A second opinion confirms the grim diagnosis, and the other doctor implies that the poisoning must have been deliberate. Bigelow remembers his drink tasted strange. With a few days to live at most, Bigelow sets out to untangle the events behind his impending death, interrupted occasionally by phone calls from Paula. She provides the first c.