The true story of a group of Cambridge University Students who are recruited to spy for the Soviet Union in the early 1930s.

In 1934, four brilliant Cambridge men are recruited to spy for Russia. Fueled by youthful idealism, a passion for social justice and a talent for lying, they take huge personal risks to pass Britain's biggest secrets to Moscow. Based on true events.

The series is set from 1934 to 1951 and follows the lives of the best-known quartet of the Cambridge Five Soviet spies, Guy Burgess, Kim Philby, Anthony Blunt and Donald Maclean, who whilst studying at the University of Cambridge are courted by Soviet agents and recruited into a world of covert intelligence and espionage. Fueled by youthful idealism, a passion for social justice, a talent for lying and a hatred for fascism, the four take huge personal risks to pass Britain's biggest secrets to Moscow. Across almost 20 years of spying and treachery, the four are bound by their beliefs, the secrets they know about one another, and the knowledge that they stand or fall together.