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.

A doctor named Dr. Fancy is charged for the death of Mrs. Sprat's son. Did he or did he not cause Mrs. Sprat's son to die.

In the future New York City, the Deputy Commissioner of Police is assisted by a robot detective in solving the murder of a scientist.