Arthur, Trillian, Random (Trillian's daughter), and Ford Prefect are all back on Earth (at least, one Earth). Grebulons are about to destroy Earth in all dimensions simultaneously by order of the Vogons. Just before they are killed, Zaphod appears in the Heart of Gold and rescues the group. The Grebulon death rays trap the group, however, and just as they are about to be destroyed Wowbagger the Infinitely Prolonged shows up to tell Zaphod he is fat arsed. Zaphod is so offended he vows to get a god to kill Wowbagger, which so pleases him that he agrees to help everyone escape the Grebulon death rays.

Zaphod heads to Asgard to get Thor to kill Wowbagger. Meanwhile, it turns out that Zaphod brought a group of Earthlings to a planet called Nano. These Earthlings follow a fake religion created by Hillman Hunter. He is currently interviewing candidates to be the god of his new planet. The Vogons, realizing there are still Earthlings left, head there to finally eradicate all humans. Random orders rubber bands in order to help kill Wowbagger when he sees him kissing his mother. Trillian and Wowbagger fall in love.

On Asgard, Zaphod is able to convince Thor to kill Wowbagger. They arrive on Nano, and Thor attacks Wowbagger, but doesn't do any damage. With Random's rubber bands, however, he is able to hurt Wowbagger badly. Just then, Arthur realizes that if Wowbagger dies, Trillian would be upset, which would be bad for Random. He convinces Thor that mercy will look better to the universe than killing Wowbagger. Thor becomes the god of Nano just in time to stop the Vogon attack. He does so, but pretends to die in order to martyr himself. Trillian and Wowbagger leave on a honeymoon. Random, Ford, and Arthur stay on Nano, with Arthur and Random becoming citizens. Ford stays to do research for the guide.

Arthur leaves on a trip to research a potential school for Random, only to be accidentally transported to a beach. There, Vogons are trying to destroy a hut he was to live in