One evening, private detective Mike Hammer (Ralph Meeker) picks up a strange woman, Christina (Cloris Leachman), who's standing on the highway wearing only a trench coat. They're stopped farther on by strangers who knock out Mike and murder Christina. Although warned not to investigate by the police, Mike and his girlfriend and assistant, Velda (Maxine Cooper), become ensnared in a dark plot involving scientist Dr. Soberin (Albert Dekker) and Christina's terrified roommate, Lily (Gaby Rodgers).