Arthur and Ford have been discovered. Vogon Captain Jeltz tortures them by reading his poetry. He then has Arthur and Ford thrown off his ship, to what must be certain death - except for one improbable miracle. At the last second, an infinite-improbability prototype ship (which can pass through every point in the Universe) rescues them. What is rather surprising is that Zaphod Beeblebrox, the hip cat who stole the spaceship, is vaguely familiar to Arthur. And so is Zaphod's companion, Trillian.

The starship Heart of Gold is headed for the planet Magrathea, a planet which it is generally agreed does not exist. In trying to land on Magrathea's surface, the crew faces an ancient nuclear missile defence system, escaping only when Arthur turns on the Infinite Improbability Drive. This helpfully replaces the missiles with a bowl of petunias and a very surprised sperm whale, who learns about the ground before he hits it. Later on, deep in the core of the planet, an unknown enemy attacks Trillian, Zaphod and Ford while Arthur meets Slartibartfast, an old man who designs planets for a living. Slartibartfast takes Arthur on a tour of the factory floor, showing off his latest project - Planet Earth, Mark Two.