The TARDIS arrives on board a Minyan space craft, the R1C, commanded by a man named Jackson. Jackson and his crew are on a long quest to recover the Minyan race banks from a ship called the P7E which left Minyos aeons ago. The Minyans are suspicious of the Doctor as they know his race of old: the Time Lords shared some of their knowledge with the Minyans, who then proceeded to destroy themselves through war as they were unable to cope with it.

The R1C is buried in a meteor storm but the Doctor helps the crew to free it. However, it then crashes into another newly formed planet at the heart of which is the P7E.

Inside the new planet the time travellers and the Minyans discover a maze of tunnels and passages. The Doctor eventually makes his way to the centre where the P7E's computer, the Oracle, holds court. The computer was originally programmed to protect the race banks but has gone insane and dominated the Minyan survivors and their descendants. The Oracle allows Jackson to take what appear to be the race banks, but they are in truth imitations containing fission-grenades. The Doctor realises the deception and obtains the real race banks. He then tricks the Oracle's guards into taking the grenades back to their leader. As there is no way of defusing them, they explode, destroying the planet and the P7E and boosting the R1C off on its voyage to Minyos II.

_{Synopsis from Doctor Who: The Fourth Doctor Handbook by David J. Howe, Mark Stammers and Stephen James Walker, reprinted with permission; further reproduction is not permitted. Available from Telo}s