A murder is committed in Cranleigh Hall. The Cranleighs ask the Doctor to play cricket and then join them for a masked ball, enabling the killer to hide in plain sight.
The Doctor stands accused, despite Lady Cranleigh knowing he is innocent. What is the secret she is protecting that allows her to let an honest man go to jail?
Deadly androids are protecting a bomb buried beneath the Earth from all investigation. However, the Doctor manages to disable it, alerting its owners – the Cybermen...
With her crew vanishing mysteriously, Captain Briggs assumes the Doctor is the guilty party, but the traitor is closer to home… as are the Cybermen.
The Cybermen are released from their silos and are on the march, attacking Briggs's crew and ensuring that the freighter remains on course for Earth. But why?
The Doctor realises the freighter is now a huge bomb and sends it back through time where it can explode millions of years ago... but Adric is still aboard...
When a Speedbird Concorde disappears back through a crack in time, the Doctor takes another Concorde to follow its trail, unaware that a mysterious conjuror, Kalid, waits for him.
After an encounter with the Plasmatons, Nyssa is possessed by strange aliens while the Doctor, joined by Professor Hayter, investigates Kalid's inner sanctum.
From within their sarcophagus, the gestalt Xeraphin are communicating through Nyssa. But their psychic energy is so powerful it may destroy her body completely.
The Master's TARDIS is repaired and the Doctor must follow him back to 20th century Heathrow, once he has rescued all the passengers and crew from both Concordes.
The Doctor tries to recuperate within the Zero Room, leaving Nyssa, Adric and Tegan to face the Master. Then Adric is taken and the TARDIS plunges towards Event One...
The Zero Room is gone and the Doctor's regeneration is dangerously unstable. To help him, Tegan locates the tranquil world of Castrovalva and the TARDIS heads there.
Something is wrong with Castrovalva, but the Portreeve cannot help the Doctor identify the problem. And the Master is taunting Adric, caught in his web of power…
As recursive occlusion threatens to destroy everything and everyone in Castrovalva, the Master's space/time trap is revealed, with Adric at its heart...
The arrival of the TARDIS is observed by three Urbankans via their manopticon devices. Intrigued, they begin dividing the Doctor's friends, and disguising themselves as humans...
As the Doctor meets the representatives of humanity aboard the Urbankan ship, a Grecian philosopher reveals a bizarre secret about Monarch and his methods...
Panicking, Tegan accidentally pilots the TARDS into space. Meanwhile Lin Fitu betrays the Doctor and Bigon to Monarch, who demands they be beheaded as punishment.
The Doctor takes a dangerous spacewalk to rescue Tegan while Nyssa and Bigon keep the Urbankans distracted. Adric decides exactly whose side he is on...
While Nyssa rests, Adric and the Doctor discover a military expedition on Deva Loka. Tegan falls asleep in the forest watched by the Kinda, but they cannot stop her dreams.
Sanders meets Panna and Karuna who leave a lasting impression on him, while the Dukkha does the same on Tegan. When Hindle's breakdown begins, the Doctor and Todd are in danger.