Parts: 4
Writer: Ian Stuart Black
Airdates: 25 June 1966 - 16 July 1966
Production Code: BB

Doctor: first
Companions: Dodo, Ben, Polly

Megalomaniac of the Week: WOTAN
Creature Feature: War Machines

Story: Amazingly, the Doctor manages to take Dodo home - London, 1966, where the schoolgirl is surprised to see that the Post Office Tower has been completed since she was last home. The Doctor, however, senses a great evil in the building, and is determined to investigate.

The Doctor and Dodo learn that the Post Office Tower is home to an amazingly powerful computer - WOTAN, for Will-Operating Thought Analogue Device - which is practically intelligent. Its creator, Professor Brett, aims to hook it up to all the other world computers, which will give it an infinite capacity for knowledge. Dodo decides to test the supercomputer by asking it what TARDIS stands for - and to the Doctor's consternation, WOTAN answers correctly.

Dodo begins hearing a buzzing sound in her head, and this is not alleviated even when Brett's secretary Polly takes her out for a night of fun at the hottest disco in town. Before long, Dodo has fallen under WOTAN's control, and the computer plans to use her to ensnare the Doctor. When WOTAN begins constructing large numbers of killer war machines, only the Doctor - along with Polly and her new friend Ben - can stop the megalomaniacal computer from taking over the world.