Small-town accountant Frank Bigelow goes to San Francisco for a week's fun prior to settling down with fiancée Paula. After a night on the town, he wakes up with more than just a hangover; doctors tell him he's been given a "luminous toxin" with no antidote and has, at most, a week to live! Not knowing who did it or why, Bigelow embarks on a frantic odyssey to find his own murderer.