The Book: Peter Jones Arthur Dent: Simon Jones Lintilla (and two clones): Rula Lenska Ford Prefect: Geoffrey McGivern Zaphod Beeblebrox: Mark Wing-Davey Bird and Footwarrior: John Baddely Hig Hurtenflurst: Mark Smith Film Commentator and Computeach: David Tate Pupil and Marvin the Paranoid Android: Stephen Moore Announcer (uncredited): John Marsh
After a brief recap, the episode opens with a conversation between Lintilla and Arthur. Lintilla mentions that she's an archaeologist, stranded on Brontitall, as her spaceship was disabled. She activates her crisis inducer, and leads Arthur through a set of tunnels. While they're running, the narrator describes the state of medical science in the universe, with artificially induced injuries.
Meanwhile, Zaphod and Ford have landed on the back of one of the birds from the previous episode, and eventually convince it to reach the ground by wrapping Ford's towel around its eyes. But because the bird had to reach the ground, it and its fellow birds are upset, and start attacking Zaphod and Ford on the surface. A loud noise occurs, which causes the narrator to explain its lack of immediate context.
Arthur emerges from a tunnel behind Lintilla, who had overcompensated for her artificially induced crisis. Lintilla introduces Arthur to two of her "sisters" (actually clones), and they begin discussing the noise, finally establishing a context for it. Lintilla finally admits that there are 578,000,000,000 clones of herself in the universe. The narrator explains how this happened, and what is being done about it. Lintilla takes Arthur to the shaft suddenly created after the mysterious loud noise, and they finally confirm what the three Lintillas had been looking for: "An entire archaeological layer of compressed shoes." After making this confirmation, they are captured by Hig Hurtenflurst, a Dolmansaxlil Shoe Corporation executive.
The narrator finally describes what made the noise and created the shaft that gave the Lintillas their breakthrough. It's none other than Marvin, who himself finally fell out of the cup that the Heart of Gold is parked in. He's lying at the bottom of a mile deep shaft, and goes "zootlewurdle." Meanwhile, Hig has decided to take Lintilla and Arthur back to his office.
Hig explains the background of what happened to Brontitall - they fell victim to a Dolmansaxlil Shoe Shop Intensifier Ray, forcing them to construct nothing but shoe shops, and selling nothing but badly made shoes. Arthur learns that Earth was to be one of the next targets, spared from this by being demolished by the Vogons. The film being shown to Arthur and Lintilla explaining the Shoe Shop Intensifier Ray is suddenly interrupted, as is power to the office, when Marvin decides to rescue Arthur and Lintilla, and her two clones.
The narrator then explains that the Shoe Shop Intensifier Ray was unnecessary, that a "Shoe Event Horizon" would have occurred on that planet, and many other worlds, as part of their natural economic histories. A lesson from the future is heard, explaining this principle. Lintilla, Arthur and Marvin continue their escape, while Ford and Zaphod finally arrive at a large, very old building, and enter it to take shelter from the still angry bird people.
They discover that the building is a spaceport, and find abandoned ships left inside it. One such ship is still connected to supply lines, and still has power. Zaphod makes himself a stethoscope (for both heads), and holds it to the hull of this ship. He's stunned by what he hears inside, and here the episode ends.