On his 38th birthday in May 1951, rising British diplomat Donald Maclean finished dinner, stepped into a waiting car, and vanished, igniting an international intelligence crisis. He was a central figure in the Cambridge Five, and his defection to Moscow exposed one of the most damaging spy operations of the Cold War.

This episode follows Maclean from a privileged, politically charged childhood and his radicalization at Cambridge to his recruitment by the NKVD and his rise through the Foreign Office. We examine how his upper-class pedigree shielded him from suspicion while he passed atomic and diplomatic secrets to the Soviets from Paris, Washington, and Cairo.

• How agent Arnold Deutsch ordered him to bury his public activism and infiltrate the establishment
• His role as secretary of the Combined Policy Committee on Atomic E ...