Not far from the sprawling grounds of Wyndham Hall, longtime MI6 agent John Repton's body is found with a bullet hole through the heart. The corpse's proximity to the estate sends ripples of concern through the intelligence community: Repton was killed while surveilling the members of a household with alleged ties to fascists--who threaten the security of the country as Hitler's control spreads across Europe. Elena Standish is assigned the case since she has a connection to the Wyndham family; Lady Wyndham's brother is courting Elena's older sister Margot.

Elena secures an invitation to Wyndham Hall for herself and a "date,"--her colleague James Allenby. To covertly investigate Repton's murder, the pair must uncover the true loyalties of the people in the house while protecting Margot from her beau's potentially dangerous relatives. But Elena is torn, for her sister has finally found happiness after years of heartbreak and sorrow, and having to take down the Wyndhams would destroy her new relationship.

As Elena and Allenby dig deeper into the Wyndham family's nefarious connections, Margot grows suspicious. Can Elena reconcile her political and professional obligations with her loyalty and love for her sister? Will Elena and Allenby get to the bottom of their colleague's murder? In The Traitor Among Us, Anne Perry raises the stakes--for Elena, MI6, and for Britain's future.