Season 1

John Vassall, a minor Foreign Office official, succumbs to his homosexual urges on a trip to Moscow and finds himself being blackmailed by the KGB into becoming one of their spies.

In 1940, Dane, Abwehr agent Hans Anderson picked up by British Intelligence and taken to Camp 020. Refusing to be a collaborate he was mentally tortured until broken. He then became part of the Double Cross network.

Bogden Stashinsky was trained to be part of the KGB's "Murder Machine" assassinating other Ukrainians. However he slowly became disenchanted with live in the Soviet Union and, with his wife, defected to the west.

In pre-war Japan, Richard Sorge, an alcoholic journalist and Communist, starts a spy ring whilst posing as a Nazi, and its activities against the Japanese continue throughout World War Two.

In 1939, Captain Best and Mayo Stevens work for SIS where they believe they were with working an anti-Hitler group who want peace. Instead their file reached Reinhard Heydrich and ultimately captured on the Dutch border.

British spymaster, William Stephenson, known as Intrepid, runs American agent Elizabeth Thorpe; code name Cynthia. Working in the Washington Embassy she seduced Vichy French officials to gain Enigma ciphers and secrets.