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.

Isherwood has a proposition; Goddard has a plan. Remembering an old song...

"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.