Arthur, Ford, Zaphod, Trillian and Marvin travel with the Heart of Gold to the legendary planet, Magrathea, the home of the planet builders. They land on the planet and set off to explore. Zaphod, Trillian and Ford explore beneath the surface, where they make a surprising discovery... Meanwhile, Arthur and Marvin are approached on the surface by Slartibartfast, who explains that the Earth was destroyed 5 minutes too early, and they intend to build a new one...