The Enterprise found the 20th-century sleeper ship SS Botany Bay and revived Khan Noonien Singh, who seized the ship before Kirk exiled him to Ceti Alpha V.
In 2267 the Enterprise found the SS Botany Bay drifting in space, a sleeper ship from the late 20th century carrying genetically engineered people in suspended animation. Their leader awoke and was identified as Khan Noonien Singh, a former ruler of a large part of Earth during the Eugenics Wars.
Khan won over historian Lieutenant Marla McGivers, revived his followers and took control of the Enterprise, threatening to kill the crew. Kirk regained the ship with McGivers's help and beat Khan in a hand-to-hand fight. Instead of putting him on trial, Kirk offered Khan and his people the chance to tame the wild planet Ceti Alpha V, and McGivers chose to go with them.
About six months later the neighboring planet Ceti Alpha VI exploded, turning Ceti Alpha V into a desert and killing many of the exiles, including McGivers. Starfleet did not check on the colony, and Khan's anger toward Kirk led directly to the events of Star Trek II: The Wrath of Khan in 2285.