Based on the true story of four brilliant young men at Cambridge University who are recruited to spy for Russia in 1934. 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...