London, 1966 — when the TARDIS materialises outside the Post Office Tower the Doctor becomes aware of a powerful and evil force nearby, so he and the ever-curious Dodo set off to investigate.
Inside the tower they track down the source of power to Professor Brett and WOTAN, his revolutionary new computer.
Designed as a universal problem solver, WOTAN has suddenly begun to think for itself and has formulated a deadly plan. Using its phenomenal power it will programme humans to build mobile fighting computers, and with these indestructible war machines WOTAN will take over the world...
