The Hitchhiker's Guide to the Galaxy recap

Arthur Dent's house is about to be bulldozed when his friend Ford Prefect, secretly an alien, reveals that the whole Earth is about to be demolished by the Vogons to make room for a hyperspace bypass. Ford hitchhikes them onto a passing ship, and after being thrown out into space the pair are improbably rescued by the stolen starship Heart of Gold, crewed by Zaphod Beeblebrox, the two-headed former President of the Galaxy, the human Trillian, and the depressed robot Marvin. They travel to the myth-shrouded planet Magrathea, where Arthur learns that a supercomputer, Deep Thought, long ago found the Answer to Life, the Universe, and Everything to be 42, and that the Earth was an even greater computer, built to discover the actual question, destroyed just before it finished. The beings behind it, who appear as mice, want Arthur's brain. He escapes with the others, and they set off for the Restaurant at the End of the Universe.

Arthur Dent wakes to find bulldozers ready to knock down his house to build a bypass. His friend Ford Prefect, who is secretly an alien, tries to explain something far more urgent: the Earth itself is about to be destroyed. A fleet of Vogons arrives and demolishes the planet to clear a route for a galactic hyperspace bypass. Ford saves Arthur by hitchhiking them both aboard a Vogon ship in the last seconds before the end. Discovered as stowaways, the two are forced to endure a recital of dreadful Vogon poetry and are then thrown out into open space.

On the edge of death in the vacuum, Arthur and Ford are picked up, against staggering odds, by a stolen starship called the Heart of Gold, which runs on an Improbability Drive that makes wildly unlikely things happen. Aboard are the ship's thief, Zaphod Beeblebrox, the reckless two-headed former President of the Galaxy; Trillian, a human woman Arthur had once met at a party on Earth; and Marvin, a brilliant but hopelessly depressed robot. The unlikely group takes stock of one another as the ship carries them onward.

Zaphod steers the Heart of Gold toward Magrathea, a planet long dismissed as a myth, whose people once grew fabulously rich by building custom-made luxury worlds for the wealthy. As the ship approaches, automated defenses launch missiles at it. The crew survives when Arthur triggers the Improbability Drive, briefly turning the incoming missiles into harmless things, and they set down on the ancient, seemingly lifeless world to look for whatever remains of it.

On Magrathea, Arthur is led away by Slartibartfast, one of the old planet designers, who explains the world's history. Long ago a race of hyper-intelligent beings built a vast computer, Deep Thought, to find the Answer to the ultimate question of Life, the Universe, and Everything. After millions of years of calculation, Deep Thought delivered its result: the number 42, an answer that meant nothing to anyone, because no one actually knew what the ultimate question itself was.

To discover the question, Deep Thought designed an even greater computer to work it out: the planet Earth, with its living creatures and people forming part of a program meant to run for ten million years. The Vogons destroyed the Earth only minutes before the calculation would have finished. Arthur learns that the beings who commissioned the Earth appear in our world as mice, and that two of them were kept by Trillian as pets. Believing the last of the program may survive inside a human brain, they set out to obtain Arthur's.

Arthur refuses to give up his brain, and the mice's attempt to take it by force is interrupted when galactic police, hunting Zaphod for stealing the Heart of Gold, storm in and open fire. The confrontation ends when Marvin, connected to the police ship's computer, so thoroughly depresses it that it shuts itself down, killing the officers. Battered, hungry, and reunited, the group escapes together aboard the Heart of Gold and decides to travel on to the Restaurant at the End of the Universe, their adventures far from over.

On Magrathea, Arthur discovers that the Earth was not simply a planet but an immense computer, built to work out the Ultimate Question of Life, the Universe, and Everything, to match the long-known Answer of 42. It was destroyed by the Vogons only minutes before it would have finished, after ten million years of running. The mice, hyper-intelligent beings who commissioned the whole experiment, decide that the last fragment of the program may be lodged in Arthur's brain and try to obtain it, first by offering to buy it and then by force. The attempt collapses when galactic police, chasing Zaphod for stealing the Heart of Gold, burst in shooting. Marvin, the depressed robot, plugs into the police ship's computer and makes it so miserable that it shuts itself down, killing the officers. Arthur, Ford, Zaphod, Trillian, and Marvin get away aboard the Heart of Gold. Hungry and shaken, they decide to go and eat at the Restaurant at the End of the Universe, leaving the question unresolved and their journey still under way.