The Tardis arrives in London, 1966, where the Doctor and Dodo visit the recently opened Post Office Tower. At its top they discover a brilliant new problem-solving super computer - the Will Operating Thought ANalogue.

But when WOTAN decides that it should rule the world, the Doctor is the only person who can stop its rampaging War Machines from destroying London. Luckily, he has the help of a young secretary called Polly and a sailor called Ben...