At a crucial Peace Conference, Sir Reginald Styles is almost assassinated.
Jo is transported to the 22nd Century where she unwittingly gives vital information to the Daleks.
The Doctor arrives in a bleak future where Earth is ruled by the Daleks and mankind is enslaved.
The Daleks travel back in time to the 20th Century to ensure that the peace conference fails.
The planet Peladon is hoping to join the Galactic Federation. But King Peladon's Chancellor has been murdered.
The work of the committee is hampered by sabotage, fear and suspicion.
The Doctor is sentenced to a fight to the death in the pit with the King's champion, Grun.
Hepesh, supported by the delegate from Arcturus, is revealed to be behind the attacks.
The Doctor and Jo visit the Master who is held prisoner on an island.
The Doctor is eager to make peace between the Sea Devils and the humans.
Jo attempts to rescue the Doctor who is being held prisoner by the Master and Trenchard.
The Doctor attempts to persuade Captain Hart of the danger that the Master represents.
The Doctor is captured by the Sea Devils and taken to their undersea base.
The Sea Devils come to the surface and attack the Naval base.
The Doctor is sent to a skybase orbiting the planet of Solos in the 30th century.
Ky flees to the planet's poisonous surface taking Jo with him while the Marshal, holds the Doctor captive.
The Doctor searches for Jo in the caves of Solos. In the shadows the mutants prepare to attack.
The Doctor and Sondergaard make an amazing discovery in the caves while Jo falls into the Marshal's trap.
The Marshal's plans for Solos go disastrously wrong. The Doctor needs to save the planet.
The Marshal is on trial, with the Doctor as chief witness. Jo and the Doctor's friends are the Marshal's prisoners.
The Master is using a device called TOMTIT to summon a creature from beyond time.
After a disastrous attempt to summon Kronos, the Master prepares to use TOMTIT once again.
The Master uses TOMTIT to summon threats from the past to attack UNIT.
The Master heads to Atlantis but he and The Doctor confront each other in the time vortex.
In Atlantis the crystal of Kronos is protected by a guardian who is half man, half beast.
With the crystal of Kronos in his possession, the Master releases the Chronovore.