Doctor Who Season 21

Tegan leaves in Resurrection of the Daleks saying she's had quite enough of all the killing. Turlough leaves in Planet of Fire when he is offered a chance to return home. Peri joins in Planet of Fire. The Doctor regenerates into his sixth persona, played by Colin Baker, at the end of The Caves of Androzani.

Episode Details

Warriors of the Deep

The Doctor and his companions arrive on Sea Base 4, a 21st century underwater nuclear missile base. The Base comes under attack from Sea Devils and Silurians, and their prime weapon a fearsome creature called the Myrka. The Silurians plan to fire the base's nuclear missiles, provoking a full scale nuclear war which will destroy mankind. Can the Doctor persuade them to try a more peaceful solution?

The Awakening

Mock wargames reconstructing the English Civil War become dangerously real, as Sir George Hutchinson begins to lose his mind, under the telepathic influence of the Malus, an evil creature entombed in the local Church since the Civil War! Tegan is forced to become the Queen of the May and is horrified when she discovers the Queen's traditional fate to be burned alive!

Frontios

The TARDIS loses its integrity and breaks apart into many pieces, stranding the Doctor, Tegan and Turlough in the far future on the remote planet of Frontios. They find a small group of humans apparently, the only survivors of the human race barely surviving after the crash of their spacecraft. They are under constant bombardment by meteors, and some of them have mysteriously disappeared. Turlough and Norna, a young female survivor, stumble across an underground cave system and start exploring it. Norna disappears and Turlough is found wandering around in a state of shock. The Doctor must try to make sense of Turlough's ramblings, and discover what is happening to the survivors and can he repair the TARDIS?

Resurrection of the Daleks

In a deserted area of the London Docks, a group of fugitives appear from thin air, and are gunned down by two menacing policemen with futuristic weapons. The Doctor detects and then follows a time corridor, and discovers that a group of mercenaries are trying to liberate Davros from his long cryogenic imprisonment on board a specially constructed prison satellite.

Planet of Fire

A young American girl, Peri, discovers a strange artifact while on holiday with her step-father in the Mediterranean. After an accident, Turlough brings her aboard the TARDIS to recover. The artefact leads the Doctor to the volcanic world of Sarn, where Turlough begins to find the natives strangely familiar. Peri is left behind on the TARDIS with Kamelion, who begins to act strangely, finally shapeshifting into the form of the Master!

The Caves of Androzani

The Doctor and Peri arrive on Androzani Minor in a vast underground cave system, where they are mistaken for gun-runners by General Chellak's soldiers. Sentenced to death, they are rescued by Sharaz Jek, a hideously disfigured ex-scientist who is plotting his revenge on Morgus, the corrupt industrialist who caused Jek's disfigurement. The Doctor and Peri find they are both suffering from Spectrox Toxoemia, a progressively fatal condition that can only be cured by the milk of a rare bat. As the effects of the Toxoemia become worse, can the Doctor find the antidote before they both die?

The Twin Dilemma

Having regenerated in order to recover from the Toxoemia, the new Doctor starts acting erratically, nearly strangling Peri and then deciding to become a hermit! He also changes clothes, exhibiting an amazing lack of sartorial taste.