|98||5A||Ribos Operation||02 Sep 1978||4||All|
|99||5B||The Pirate Planet||30 Sep 1978||4||All|
|100||5C||The Stones of Blood||28 Oct 1978||4||All|
|101||5D||The Androids of Tara||25 Nov 1978||4||All|
|102||5E||The Power of Kroll||23 Dec 1978||4||All|
|103||5F||The Armageddon Factor||20 Jan 1979||6||All|
Romana joins as a companion at the request of the White Guardian at the start of the season to assist the Doctor in locating the six segments of the Key to Time.
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 megalomaniac 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 realizes that the Marshal is being hypnotically controlled, and has to confront the evil Shadow, a servant of the Black Guardian!