CIA officer Daniel Miller arrives in Berlin on a clandestine mission to unearth an anonymous whistle blower, alias Thomas Shaw, and reunites with his old friend Hector DeJean. As Daniel gets closer to Shaw, his quarry reacts in a murderous fashion.

Frost and Kirsch worry their secrets will be unearthed when Langley investigators sweep Berlin Station to ferret out fodder for future Shaw leaks. Meanwhile, Daniel's hunt for the mole is put at risk.