Watch D.O.A.

This motion picture begins with a man who walks into a police station and tells the officers he wants to report a murder, his own. The entire movie is a flashback of how, as a small town accountant, he went to San Francisco for a weekend of fun before settling down with his fiance. He wakes up the next morning with a stomach pain, and the doctor tells him somebody slipped him a deadly toxin at the bar. The doctor also tells him there is no antidote, so basically somebody just murdered him. He must find out who and why.