Winter, 1947. Britain’s secret services have been penetrated. The country is more vulnerable than ever – and Soviet leader Joseph Stalin knows it. He decides it is time to send his master of ‘Special Tasks’ to create extra chaos. But Stalin has a more important motive than mere disruption. He has a man on the inside who must be protected at all costs – a communist super-spy who has the secrets of the atomic bomb at his fingertips. Freya Bentall, a senior MI5 officer, no longer knows who to trust and is left with one option: to bring in an outsider whose loyalty is beyond question – Cambridge professor Tom Wilde. His task: to find the traitor in MI5. Bentall has three main suspects and Wilde must get close to them all.