Restless femme fatale Florence Carala (Jeanne Moreau) recruits her lover, Julien Tavernier (Maurice Ronet), to murder her wealthy husband, Simon (Jean Wall), in his office and make it appear like a suicide. Tavernier does the dirty deed eagerly, but becomes trapped in an elevator when he returns to remove a key piece of evidence he had accidentally left behind. Tavernier's unfortunate oversight sets into motion a dark ripple of events that bloodies the cold Paris night.