On the planet Minot, the Second Doctor discovers a seemingly abandoned space carrier. He's trapped aboard when the Cybermen reveal themselves and lift off in the carrier. Discovering they plan to destroy Earth with a bomb, the Doctor primes the bomb but only has twenty-five minutes to escape. He is pursued by the Cybermen until he's trapped within the bomb, before escaping and using one of their patrol craft to flee. Before the Cybermen can train their guns on him, the ships explodes. He returns to Minot and leaves with John and Gillian.