1949. The Cold War is tightening its grip, spies lurk in every shadow, and the race for the atomic bomb is reaching a deadly pitch.

When GCHQ operative Beattie Cavendish is sent to a pivotal listening station in a remote corner of the Scottish Highlands, she finds a base in chaos - its commander missing, its mission compromised, and whispers of a German spy ring closing in. But Beattie's task takes a darker and more personal turn when her uncle vanishes nearby, leaving behind a chilling note: I know who you really are.

With private detective Patrick Corrigan at her side, Beattie must uncover the truth before snow and secrecy seal them in. For here, betrayal runs deep, and no one is who they seem.