Parts: 4
Writers: Bob Baker and Dave Martin
Airdates: 7 January 1977 - 28 January 1978
Production Code: 4Y

Doctor: fourth
Companions: Leela, K-9 mark one

Story: Materializing at the edge of the cosmos, the TARDIS is caught in a spiral nebula, forcing the Doctor to rematerialize onto the nearest spacecraft to escape the strong gravitic pull. But the craft on which the Doctor, Leela and K-9 arrive is an anomaly...it appears to be a Minyan craft, from the planet Minyos. But the Minyan civilization was destroyed 100,000 years ago, after the Time Lords, in their pre-nonintervention days, gave the Minyans advanced technology that enabled them to learn to annihilate themselves. So, Leela wonders, even if a ship of Minyans escaped before their planet was destroyed, how can any of them possibly still be alive?

As it turns out, thanks to Time Lord regeneration technologies, all of the crew are still alive, each having regenerated over 100 times. Their mission: tracking down the colony ship P7E, which was intended to take the Minyan race banks to a Minyos II, where their race could start afresh. Jackson, the captain of the Minyan ship, and his crew have been tracking the P7E for 100,000 years - and they find it at the center of the spiral nebula.

During the years that the P7E has been trapped at the core of a new planet in the nebula, the descendants of the Minyans have become slaves. Under the direction of their overlords, the Seers, they dig out the rock around the ship in order to provide fuel and power for their ruler, the mechanical Oracle. Any suggestion of rebellion is met with the severest punishment, and trigger-happy guards roam the caves. The Doctor and Leela must help Jackson and his crew to reach the P7E and find the race banks, and maybe liberate the slaves in the process...but the Oracle has other ideas.