The Restaurant at the End of the Universe continues the story of Arthur Dent; Trillian, his sometime girlfriend; Zaphod Beeblebrox, president of the Imperial Galactic Government; Marvin the depressed robot; and Ford, his longtime hitchhiking companion. The Heart of Gold is speeding away from Magrathea, the adventurers having barely escaped there with their lives at the end of The Hitchhiker’s Guide to the Galaxy.

Arthur inadvertently overloads the computer’s systems by asking for a good cup of English tea. When the approaching Vogon ship, sent to kill Arthur and Trillian because of their ties with Earth, opens fire on the Heart of Gold, the computer is so focused on brewing a pot of tea that it cannot devote the needed resources to provide an adequate defense. The characters once again narrowly escape what appears to be certain death when Zaphod manages to summon his great-grandfather to bail them out.

As a result of that rescue, Zaphod and Marvin mysteriously disappear from the ship, finding themselves in the offices of The Hitchhiker’s Guide to the Galaxy, the self-proclaimed repository of all knowledge. After Zaphod and Marvin make it past the existential elevator to find the office of Zarniwoop, Zaphod realizes why his great-grandfather sent him there—he was reminding Zaphod that he is in fact searching for the man who runs the universe.

Zaphod is transported to Frogstar World B, the most evil planet in the universe, and subjected to the Total Perspective Vortex. The Vortex reveals to its victims the entire scope of the universe and the excruciatingly small part that they play in it. It invariably destroys the viewer, demonstrating the high moral lesson that in order to survive as a sentient being one must not have too strong a sense of proportion. Yet Zaphod learns he is not the least but the most important thing in the universe because his universe was created especially for him by Zarniwoop. The two together continue the search, in the real universe, for the man who rules the universe.

Zaphod, Trillian, Arthur, and Ford end up, astonishingly, in Milliways, the Restaurant at the End of the Universe, an entertainment emporium that takes advantage of deep pockets and cataclysmic upheavals of matter. It and its counterpart, the Big Bang Burger Bar, use time travel to provide customers with the experience of the two biggest events in the history of the universe: its creation and its demise. After dinner and a brief brush with death, Zaphod and Trillian materialize back on the Heart of Gold, now piloted by Zarniwoop. They travel across space propelled by the ship’s Infinite Probability Drive and land on the planet of the ruler of the universe. After a disappointing chat, they leave Zarniwoop behind to cope with the unimpressive ruler.

Arthur and Ford find themselves in a strange spaceship peopled with the unwanted exiled third of a distant planet’s population. After crash-landing with the outcasts, they wander around for a while, meeting some creatures clearly in need of evolution’s guiding hand. Arthur and Ford eventually recognize that they are on prehistoric Earth. The outcasts quickly create committees, subcommittees, documentaries, and management meetings which enable them to declare war on an uninhabited continent and declare tree leaves legal tender. Ford realizes that the prehistoric people are sadly dying off, leaving the crash-landed bureaucrats as the sole ancestors of the human race.

The book concludes with Zaphod and Trillian chatting purposelessly with the ruler of the universe, Arthur and Ford celebrating with humankind’s ancestors at a management party, and Marvin missing and unaccounted for.