Living in exile on the planet Vulcan, the ragtag former crew of the USS Enterprise steal a starship after receiving a planetary distress call from Earth: a space probe has entered into orbit around Earth, disabled global power on the planet and evaporated the oceans. Captain Kirk (William Shatner), Spock (Leonard Nimoy) and the rest of the officers travel back in time to retrieve now-extinct humpback whales, which Spock has deduced will communicate with the probe and send it away from Earth.