UNIT is providing security cover at an experimental drilling project at Eastchester, designed to penetrate the Earth's crust and release a previously untapped source of energy. Soon, however, the drill head starts to leak an oily green liquid that transforms those who touch it into vicious primeval creatures with a craving for heat. The Doctor is accidentally transported "sideways in time" by the partially repaired TARDIS control console into a parallel universe where the drilling project is at a more advanced stage. Thwarted by his friends' ruthless alter egos, he works to save both universes.

To escape from the volcanic eruption on Dulkis, the Second Doctor uses an emergency unit. It moves the TARDIS out of normal time and space. The travellers find themselves in an endless void where they are menaced by white robots. Having regained the safety of the TARDIS, they believe they have escaped — until the ship explodes. They find themselves in a land of fiction, where they are hunted by life-size clockwork soldiers and encounter characters like Rapunzel, the Karkus, and Swift's Lemuel Gulliver.

A dramatised impression of the events surrounding the Electrical Trades Union ballot rigging case of the late 1950s and early 1960s.