The Doctor and Dodo return to London in the present day where the Doctor becomes concerned about WOTAN, a new super-computer installed in the Post Officer Tower.

Dodo is under the control of WOTAN and attempts to lure the Doctor into a trap, while the rest of WOTAN's slaves begin construction on its robotic War Machines.

Ben tries to escape from the warehouse but is captured by Polly, who is now also under WOTAN's control, and forced to work on construction the War Machine.

The first War Machine is defeated but the Doctor only has a matter of hours to destroy WOTAN before the rest of its army is activated.