Kerwin Matthews, playing a dissolute drifter down on his luck, Jeff Farrell, is stranded in a cheap bar in France where he falls for Annette, the proprietor's pretty stepdaughter, played by Liliane Brousse. Annette's stepmother Eve, played by Nadia Gray, gradually shifts the young man's attentions to herself, rather than her stepdaughter, and together Eve and Jeff concoct a plot to help free Eve's estranged husband from the institution in which he's been confined as a homicidal maniac these past four years after committing the so-called "Acetylene Murder", when he killed with a blowtorch the man who raped Annette. The idea is that Georges, the husband, will leave the country, but, unknown to Jeff, it's not Georges who escapes but Henri, the guard who has become Eve's lover . . .