The show was based off the book and radio show of the same name. It told the story of Arthur Dent, an average Englishman who life was spared by his friend, who turned out to be an alien, while the planet Earth is destroyed. His friend tells him about the Hitchhiker's Guide to the Galaxy, a guide with anything you ever needed, and wanted to know. They travel across the galaxy, meeting friendly, and not so friendly characters in order to find the great question (the answer being 42).
Ford and Arthur dash to the escape pods, where they end up being teleported to a mysterious ship, "Ark B". Which they discover is a ship filled with middle-men trying to find a world to colonise, and the world they have chosen is Earth, 2 million years in the past. Arthur and Ford are now stuck on prehistoric Earth.