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The Enterprise is chosen to participate in the secret experimental testing of the M-5, a supercomputer that is designed to replace the human leaders of a starship, in this episode of the popular 1960s science fiction series. Kirk reluctantly agrees to temporary hand over his command for the duration of a test exercise, to allow the computer to prove itself amidst Starfleet military drills. A programming oversight, however, causes the M-5 to mistake the practice exercises for actual combat, leading to the destruction of a friendly vessel. Additionally, the Enterprise crew discovers that the computer will not return power to human hands or allow communication with other vessels who are unaware of the experiment. Captain Kirk and the others must discover a way to regain control of the ship or else face destruction as a rouge vessel at the hands of their own colleagues.