London 1909: The British Empire seems invulnerable. But Captain Vernon Kell, head of counter-intelligence at the War Office, knows better. In Russia, revolution; in Germany, an arms race; in London, the streets are alive with foreign terrorists. Kell wants to set up a Secret Service, but to convince his political masters he needs proof of a threat - and to find that, he needs an agent he can trust. The playing fields of Eton may produce good officers, but not men who can work undercover in a munitions factory that appears to be leaking secrets to the Germans.