In the mid-22nd century, mankind has begun colonizing the far reaches of the universe. Armed with artificially intelligent "Thermostellar Triggering Devices," the scout ship Dark Star and its crew have been alone in space for 20 years on a mission to destroy "unstable planets" which might threaten future colonization of other planets.The ship is in a state of deterioration and there are frequent system malfunctions (for example, an irreparable radiation leak, their cargo of intelligent talking bombs lowering from their bomb bay without a command to do so, and an explosion destroying their sleeping quarters), and only the voice of the ship's computer for company. The Dark Star′s commanding officer, Commander Powell, was killed during hyperdrive as a result of an electrical short-circuit behind his rear seat panel, but remains aboard the ship in a state of cryogenic suspension. The ship's remaining crew consists of its new commanding officer, Lieutenant Doolittle (helmsman, and originally second-in-command), Sergeant Pinback (bombardier), Corporal Boiler (navigator), and Talby (target specialist). As the tedium of their tasks over 20 years has driven them "around the bend", they have created distractions for themselves: Doolittle, formerly a surfer from Malibu, California, has constructed a musical bottle organ; Talby spends his time in the ship's observation dome, content to watch the universe go by; Boiler obsessively trims his mustache, smokes cigars, and shoots targets with the ship's emergency laser rifle in a corridor.Pinback plays practical jokes on the crew members, maintains a video diary, and has adopted a ship's mascot in the form of a mischievous "beach ball"-like alien who refuses to stay in a storage room, forcing Pinback to chase it around the ship and eventually kill it with a gun. Pinback claims he is actually liquid fuel specialist Bill Frug, who inadvertently took the "real" Sergeant Pinback's place after he committed suicide by jumping into a fuel tank.En route to their next target (the Veil Nebula[6]), the Dark Star is hit by a bolt of electromagnetic energy during a storm, resulting in yet another on-board malfunction, with "Thermostellar Bomb #20" receiving an order to deploy. The ship's computer convinces Bomb #20 that the order was in error, and persuades the bomb to disarm itself and return to the bomb bay. Talby notes the malfunction, and investigates the fault. He discovers a damaged communications laser in the emergency airlock while the crew is engaging in their next bombing run. While Talby attempts to repair it, the laser malfunctions, blinding Talby and knocking him unconscious, causing extensive damage to the main computer, and damaging the bomb release mechanism on Bomb #20.Due to the damage to the ship's computer, the crew members cannot activate the release mechanism and attempt to abort the drop. After two prior accidental deployments, Bomb #20 refuses to disarm or abort the countdown sequence. The computer activates dampers to confine the blast to a diameter of one mile, but that is all it can do at the moment. As Pinback and Boiler try to talk the bomb out of blowing up underneath the ship, Doolittle revives Commander Powell, who advises him to teach the bomb the rudiments of phenomenology. After donning a space suit and exiting the ship to approach the bomb directly, Doolittle engages in a philosophical conversation with Bomb #20 until it decides to abort its countdown and retreat to the bomb bay for further contemplation.