Angleton unearths a mole in the British Embassy; Maclean is identified as a suspect.
Maclean passes U.S. nuclear secrets to the Russians, who surprise the world by exploding their first atomic bomb.
Donald marries an American as the Germans close in; the spies return to the side of the Allies once again.
The men try to bury their left-wing pasts; Anthony Blunt exploits his connections with the Royalty.
In 1934, Soviet agents recruit four students into the world of covert intelligence and espionage.