Conclusion. The West is stunned when Russia detonates an atomic bomb years ahead of schedule, leading to Angleton's discovery of a mole at the British Embassy. The future of the ring now in doubt, an escape plan is organized for two of the spies.
Part 4. Maclean reveals the truth about his double life to Melinda (Anna Louise Plowman); Philby alerts the KGB to a Russian defector; Blunt befriends King George VI (Anthony Andrews), who gives him a “hush-hush” assignment; British intelligence suspects a mole in its midst.
Part 3 of five. Philby is unable to complete his assassination mission and joins MI5; Maclean falls for an American (Anna Louise Plowman) as the Nazis overrun France; worries arise over Burgess's volatile behavior; Blunt reconsiders his life as a double agent. Angleton: John Light.
Part 2 of five. After his mission to rescue a Jewish professor ends tragically, Philby impulsively proposes to Litzi. But the demands of his KGB service threaten their union. As Philby wrestles with his conscience, Burgess, Blunt and Maclean ensconce themselves within the British establishment.
Part 1 of five. Idealistic Kim Philby (Toby Stephens) is recruited by a pair of fellow dons to spy for the KGB. His first task: convince a well-connected chum to join the ring. Donald Maclean: Rupert Penry-Jones. Guy Burgess: Tom Hollander. Anthony Blunt: Samuel West.