Elevator to the Gallows (1958)

Florence Carala and Julien Tavernier, ensnared in a dangerous affair, devise a plan to kill her husband, Simon, a wealthy industrialist and Julien's boss. Using his military skills, Julien executes the perfect murder, making it appear as a suicide. But a single, overlooked detail forces Julien back into the building, where he becomes trapped in an elevator.