|Edition: || UK|
|When: ||June 1995|
|Format: ||1 x VHS PAL|
The Doctor, Romana and K-9 continue their search for the six disguised segments that make up the powerful Key to Time.
The TARDIS brings the Doctor and Romana to Delta 3, the third moon of the planet Delta Magna. Romana is captured by the Swampies, the original inhabitants of Delta Magna, displaced from their home world by human colonists. They intend to sacrifice Romana to their god, the mighty Kroll.
The Doctor's search for his companion brings him to a massive refinery in the middle of the swamp, which is extracting protein from under the water to feed the people of Delta Magna. The Doctor is mistaken for Rohm-Dutt, an amoral gun-runner who is supplying the Swampies with weapons to aid them in their plan to attack the refinery and force the workers to leave Delta 3.
The Doctor escapes the refinery in time to rescue Romana from the sacrificial altar, discovering in the process that Kroll is just a myth, a story to frighten children. They resolve to find the Fifth Segment and leave the moon, avoiding the intrigues of the refinery workers and the attentions of the fanatical Swampies.
However, all is not as it initially seems. What is stirring on the floor of the swamp and can the instruments on the refinery really be correct in saying that it is five miles across? The Doctor realises that Kroll is more than a mere legend and its centuries-long slumber has been disturbed by the refinery. Now it is awake, the time-travellers find that it is very large, and very hungry...
Originally transmitted 23rd December 1978 - 13th January 1979.