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

Daniel and Hector embark on a dangerous operation to track down Shaw. Meanwhile, Valerie finds out the truth behind Iosava, and Frost and Kirsch deliberate future plans for themselves and the rest of Berlin Station.

Daniel teams up with Esther Krug of the BfV to prevent the next Shaw leak involving a foreign defector. Valerie and Robert spar over strategy as her investigation into Iosava gains traction; Hector gets a late-night visit from Shirley Pimple.

Valerie's investigation into Aleksandre and Ruth Iosava comes to a head in a German/American sting Operation involving Clare Itani, a CIA Officer and Hector’s lover. Langley's unannounced participation moves things from bad to worse.

Frost must pick up the pieces after the Iosava Operation goes sour while Robert explores a different angle. Hector goes rogue but brings Daniel with him, preempting a crucial moment of clarity.

Repercussions from the Iosava debacle leave Frost in the shadows and the Station in disarray as Robert embraces a new role. Hector finds himself in the hot seat, Valerie reveals a secret of her own––and Daniel inches closer to the truth.

The mystery of Shaw's true identity finally solved, Daniel confronts his own conscience as he learns the origins of "Thomas Shaw"; Valerie’s suspicions about Robert further escalate rising tensions between them, and Kelly Frost suddenly becomes an integral part of the team.

Daniel assembles the crew as they piece together the extent of Langley's involvement in the Iosava rendition. Steven and Kelly Frost reunite against the odds; Hector pursues a new approach for his atonement – and the Thomas Shaw mantle is passed.