Gallifrey, world of the Time Lords. The Doctor returns and claims the vacant presidency. But his behaviour is erratic and his motives mysterious.

The Doctor is made president of the Time Lords. He immediately orders K-9 to lower the planet's defences and has Leela banished to the wilderness.

The Doctor has betrayed his own people and enabled a Vardan invasion of Gallifrey. Leela joins forces with the Outsiders and prepares to strike back against the aliens.

The Doctor works to free his planet of the Vardan menace. How can he defeat an enemy who can read his very thoughts? And does their invasion conceal a greater menace?

The Sontarans have invaded Gallifrey, seeking to seize the incredible power of the Time Lords. The Doctor's first step is to cut them off from their fleet. But Kelner is helping the enemy…

The Sontarans finally invade the TARDIS itself, seeking the Great Key. The Doctor, however, has other uses for this powerful object…

Paris, 1979. The Doctor and Romana are here on holiday, but something is disturbing the flow of time. Could the time travel experiments of Count Scarlioni be to blame?

Captured by the Count, the Doctor and Romana uncover an elaborate plan to steal the Mona Lisa. But there is more to Scarlioni's plans than a simple theft.

The Doctor and Romana unwrap an intricate plot involving aliens, time travel and the Mona Lisa. How is Count Scarlioni living in two times at once? And what does he want?

Scaroth is determined to go back 400 million years in time to prevent a mistake. But the Doctor must stop him – because the consequences would be disastrous.