There has been a series of mysterious vanishings on the desert planet Chronos in the 33rd century. Survey teams working for a university seem to have simply vanished amongst the pyramids on the planet. Alongside two other survey teams and an expert on cybernetics, the Doctor and Evelyn learn the deadly truth: that the planet Chronos is being used as a base for one of the Doctor's oldest and deadliest foes — the Cybermen.

The planet is under Cyber control. Why do they want the TARDIS? The Controller's plan becomes clearer.

"Friendship is your downfall, Doctor." Playing God with time as your toy. The Controller's influence is strong.

Hiding among Cybermen. Morality is a luxury. A bit of sabotage.

The temporal wave hits. Considering the future. The historic flight.