Frank G. Wheatley is a British spy who is investigating the past of Lydia Constantine, the widow of a secret agent. Constantine is suspected of selling Cold War secrets to the Communists. To ascertain the truth, it is necessary to ""rebuild"" Constantine and send his living counterpart behind the Iron Curtain.

A man who dies on an operating table is brought back to life, but he has no memory of anything that happened before he wakes up. A government agent decides that he would make a perfect undercover operative.