In the wake of Kim Philby’s escape to Moscow, his closest friend in Britain’s Secret Service, Nicholas Elliott, is under investigation.

Investigator Lily Thomas understands that Elliott is never going to divulge anything of value in a conventional interrogation process so she manipulates him.

Philby begins to understand that the KGB can never fully trust him now that he’s in Moscow, and as far as they’re concerned, his life as a spy for them is over.

Elliott rattles Blunt’s cage to make him panic and then follows him to a clandestine meeting in the middle of the night.

Elliott and Lily fear that no one can be trusted. They must get to Blunt before anyone else to interrogate him and confirm their suspicions.