Elena Standish investigates the murder of a fellow MI6 agent near the country estate of one of England's most influential families, in this gripping mystery from New York Times bestselling author Anne Perry.

Not far from the sprawling grounds of Wyndham Hall, the body of longtime MI6 agent John Repton is found, shot dead with a single bullet to 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 influence spreads across Europe. Elena Standish is assigned the case, thanks to her new connection to the Wyndham family: Her older sister, Margot, is being courted by Lady Wyndham's brother.

Elena secures an invitation to Wyndham Hall for herself and a companion—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 widowed sister has finally found happiness after years of sorrow, and having to take down the Wyndhams would destroy Margot's 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 uncover their colleague's killer? In The Traitor Among Us, Anne Perry raises the stakes—for Elena, MI6, and the future of Britain.