Season 16 episodes

No   Code   Title                    First Shown  Eps  Exists
-------------------------------------------------------------
 98   5A    The Ribos Operation        2 Sep 78    4    all
 99   5B    The Pirate Planet         30 Sep 78    4    all
100   5C    The Stones of Blood       28 Oct 78    4    all
101   5D    The Androids of Tara      25 Nov 78    4    all
102   5E    The Power of Kroll        23 Dec 78    4    all
103   5F    The Armageddon Factor     20 Jan 79    4    all

Notes:

Romana joins as a companion at the request of the White Guardian at the start of the season.

Episode Details

The Ribos Operation

The Doctor is given the task of reassembling the six parts of the Key to Time at the behest of the White Guardian. He and his new companion Romana, go to the icy world of Ribos in search of the first segment where they encounter a pair of con-men and a megalomanic ex-tyrant.

The Pirate Planet

The locator leads the Doctor and Romana to the planet Calufrax, or rather its location since it no longer appears to exist. In its place they find a hollow planet called Zanak, ruled over by a mysterious queen called Xanxia and her henchman, an evil one-eyed captain.

The Stones of Blood

The Doctor and Romana arrive at a circle of standing stones in the English countryside. They meet an elderly lady professor and her companion who are involved in a study of the stones. However when two campers and the local Druid priest are all killed by one of the stones, the Doctor suspects all is not as it seems, but can he warn Romana in time?

The Androids of Tara

The Doctor and Romana arrive on the planet Tara, a planet with a medieval social structure but the technology to build and maintain sophisticated androids. Romana is mistaken for an android replica of the Princess Stella, and they are soon embroiled in the the plans of an evil Count to seize the throne.

The Power of Kroll

The locator leads the Doctor and Romana to the third moon of Delta Magna. The moon is a swamp covered world on which a small crew of humans maintain a refinery and are in constant feud with the simpler humanoid creatures known as swampies who also live there. Their God, a giant octopus like creature called Kroll makes an appearance and threatens the refinery...

The Armageddon Factor

The Doctor and Romana arrive on the planet Atrios looking for the crucial final segment. Atrios and the nearby planet Zeos are waging an interplanetary nuclear war, which has already killed most of the Atrions. Despite this, the Marshal of Atrios is preparing for a fanatical last strike that will utterly destroy Zeos, against the wishes of the Peace movement headed by the Princess Astra! The Doctor realises that the Marshal is being hypnotically controlled, and has to confront the evil Shadow, a servant of the Black Guardian!