The TARDIS arrives in London in 1966 and the First Doctor and Dodo visit the Post Office Tower. There they meet Professor Brett, whose revolutionary new computer WOTAN (Will Operating Thought ANalogue) can actually think for itself and is shortly to be linked up to other major computers around the world — a project overseen by civil servant Sir Charles Summer. It transpires, however, that WOTAN considers humans to be inferior and believes they should be ruled by machines. Exerting a hypnotic influence, it arranges the construction of War Machines — heavily-armed, self-contained mobile computers — with which to take over the world.