When Philip and Elizabeth are given an urgent task to plant a bug in Defense Secretary Caspar Weinberger's office, they risk exposure when an unwilling maid of the Weinberger home refuses to cooperate. Stan closes in on a member of the Soviet Rezidentura in an effort to uncover the identities of deep cover Directorate S operatives.

A mole hunt within the KGB causes suspicion amongst allies and shatters trust within the Jennings' marriage. Meanwhile, Stan's plan to keep his mole safe puts her at even greater risk of discovery.

Philip and Elizabeth must stop an assassin from taking out key US scientists, while Stan and the FBI hunt the same man. Grannie shocks Elizabeth with the truth of what happened between Philip and Irina in New York.

Philip and Elizabeth are put to the test when a routine mission goes horribly wrong. Stan and the FBI are pushed to their limit when one of their own goes missing.

No one is safe as Philip and Elizabeth evacuate their children while trying to complete the mission. Stan holds Nina's future in his hands.