Dirty Hands (1975)

Saint Tropez, 1975. Julie Wormser and her neighbour Jeff Marle, a writer, are lovers. They plan the assassination of Julie's wealthy husband Louis, an impotent who drinks a lot. She hits Louis, and leaves the rest of the task to Jeff. She finds herself alone the following day, and becomes the prime suspect. Where is Louis' body? Where is Jeff? Is there any secret beyond a door?