Einer muß die Leiche sein (1978)

A group of tourists from the GDR spend their holiday at the coast of Bulgaria. When making a trip to a small fisher house, they have to stay they night, because the ship's motor broke down. One of the group proposes a game: Someone has to be a corpse, one the detective and another one the murderer. But shortly after starting the game the "corpse" has vanished only to befound at the foot of the nearby cliff - being dead for real. Now the group start their investigation...