The crew of the Dark Star are on a 20-year mission to destroy unstable planets and make way for future colonisation. The smart bombs they use to effect this zoom off cheerfully to do their duty. But order prevails, the nerves of this crew are becoming increasingly frayed to the point of psychosis. Their captain has been killed by a radiation leak and when an asteroid storm causes a malfunction, Bomb Number 20 (the most cheerful character in the film) has to be a repeatedly talked out of exploding prematurely.