The Book: Peter Jones Arthur Dent: Simon Jones Ford Prefect: Geoffrey McGivern Zaphod Beeblebrox: Mark Wing-Davey Eddie the Computer: David Tate Trillian: Susan Sheridan Recorded voice and Slartibartfast: Richard Vernon Whale (uncredited) and Marvin the Paranoid Android: Stephen Moore Announcer (uncredited): John Marsh
The episode begins with a narration describing the significance of Magrathea, a planet that long long ago manufactured custom-designed planets for rich businessmen. Due to its immense success, Magrathea became the richest planet in the galaxy and the galactic economy collapsed. Ford and Zaphod argue about the accuracy of this legend, Ford believing that it is nonsense, Zaphod believing he has found the long-lost planet.
As the ship orbits the planet, it triggers an automated recorded message, from the Commercial Council of Magrathea, that notes that Magrathea is currently closed for business, and to leave. A follow-up message announces that nuclear missiles will be launched against the ship.
The missiles are detected, and the crew struggle to get the Heart of Gold to escape the missiles. Disaster is averted when Arthur activates the Infinite Improbability Drive and the missiles are turned into a bowl of petunias and a very surprised-looking sperm whale. Trillian notes that her white mice (that she had taken with her from the Earth) have escaped.
The ship lands, and Ford, Arthur, Zaphod, Trillian and Marvin go onto the surface. (The episode, as released on CD, is edited here to avoid possible musical copyright concerns. ) They split up, and Zaphod, Trillian and Ford explore a tunnel, noting that they seem to be following the mice, whilst Arthur and Marvin are left on the surface as lookout. Eventually, Slartibartfast comes to meet Arthur, and takes him into the interior of the planet, leaving Marvin behind. Inside Magrathea, he shows Arthur a planet that they are working on at the moment. Arthur recognises it as the Earth. Slartibartfast explains that the original Earth had been destroyed five minutes too early, and they are constructing a replacement. The original Earth had apparently been commissioned by some mice in order to find the "Ultimate Question".
Notes: First appearance of Slartibartfast. A reference by Arthur to Pink Floyd being played by Marvin is often cut out of this episode.
Music: Kotakomben from Einsteig by Gruppe Between; Space Theme from Go by Go; Equinoxe by Jean Michel Jarre; That's Entertainment; Shine On You Crazy Diamond by Pink Floyd*; Rock and Roll Music by The Beatles*; Wind On Water from Evening Star by Fripp and Eno; Over Fire Island from Another Green World by Brian Eno[6]
* denotes music from the portion of the episode removed from CD releases.