Parts: 3 (45-minute)
Writer: Robert Holmes
Airdates: 16 February 1985 - 2 March 1985
Production Code: 6W

Doctors: second, sixth
Companions: Jamie, Peri

Creature Feature: Androgums, Sontarans

Story: The Time Lords send the second Doctor and Jamie to space station Chimera in the third zone, to investigate and put a stop to the illegal time experiments of professors Kartz and Reimer. But no sooner has the Doctor begun to beseech his old acquaintance Dastari than the station is attacked by Sontarans. The potato-headed aliens are being aided by Shockeye and Chessene, two of the Androgums on the station. While Jamie escapes, the Doctor is captured...

...and elsewhere in time and space, to Peri's alarm, the sixth Doctor collapses. When he recovers, he is left with the disturbing impression that somewhere, he is being executed. Spurred on by Peri's suggestion that he get medical aid, the Doctor decides to pay a visit to geneticist Dastari. When they arrive on the station, things have changed. Shockeye's once-pristine kitchen is filthy, corpses are strewn throughout the corridors, and the computer decides it needs to kill them. When Peri finds a savage Jamie lurking in the bowels of the station, the Doctor makes a connection.

After a telepathic communication, the sixth Doctor learns that the second has been taken to Seville, so he, Peri and Jamie follow. There they discover that Dastari, Shockeye and Chessene have enlisted the help of the Sontarans to dissect the Doctor and take his symbiotic nuclei. With this, the secret of safe time travel will be theirs, and they will be free to control the universe...