The Sleeping Car Murder (1965)

Six people travel by train overnight from Marseilles to Paris. When the train arrives at its destination, one of the engers, a girl, is found dead in a sleeping berth. The police led by Inspector Grazzi investigate the other five engers, suspecting that one of them was responsible. However, as the investigation is stepped up, the other engers start turning up dead. It is then up to the last remaining two to solve the case, before they become the next victims.