Arthur Dent, a perfectly ordinary Earthman, is surprised to wake up one day to find bulldozers outside his house with orders to knock it down to build a by-pass. He is even more surprised later on in the pub when his best friend Ford Prefect reveals himself to be from a small planet somewhere in the vicinity of Betelgeuse. The two are forced to hitch a lift on one of the advancing Vogon spacecraft which proceed to blow up the Earth to make way for an interspace bypass. Our two heroes find themselves trapped in a storage room in hyperspace, with only a menacing Vogon guard for company.

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.