Phillip and Elizabeth Jennings are two seemingly normal Americans who are really undercover KGB agents. After kidnapping a Soviet defector they discover their new neighbor is an FBI agent assigned to their case.

Gregory, Elizabeth's lover, helps them make contact with Robert's widow despite an FBI team. Gabriel's replacement shows up. Phillip then makes a dangerous buy of information.

An Air Force colonel offers to sell SDI secrets to the KGB. Viola reports the bug in the Weinberger home. Phillip agrees to marry Martha hoping she'll continue spying while Nina confesses to spying for the Americans.

Elizabeth and Phillip are at risk of getting caught when they fear their assignments may be a set-up. Stan is convinced he'll find Nina a way out.

Just when Philip and Elizabeth think they have a quiet road ahead, an old friend returns to complicate things. Not only do they have to intercept a target who could prove valuable to the Soviet Union, but they also have to take on an important rogue mission without the support of the Centre. Divisions inside the Rezidentura deepen between Oleg and Arkady, and there's an upheaval at the FBI as the chickens come home to roost for Agent Gaad. Meanwhile, Martha's frustrations threaten to blow Philip's cover.

Philip and Elizabeth both find themselves faced with painful turns in their various missions. Stan fights to gain access to an American military program that could give him the upper hand in his battle of wills with Oleg.

Tensions simmer between Philip and Elizabeth as they disagree over handling orders from the Centre. When Elizabeth loses key intel, Philip enlists Annelise on a mission with an unexpected outcome.

Elizabeth and Philip come together to deal with a mission gone wrong, but struggle to reconcile their ideologies; Stan welcomes a Soviet defector to America; Nina acclimates to her new living arrangements.

Elizabeth and Paige take a trip that lands them in treacherous territory.

The Centre rushes to prepare Martha's exfil as Directorate S agents try to locate her but, it seems that a backup transport was also ordered. FBI tears up the Clark Westerfeld apartment. Martha almost walks into the FBI dragnet. Philip is overcome with self-recrimination...KGB may kill Martha. The FBI intercepts a call to Martha's parents from Woodley Park and stake out the area. Philip gets a call from Rock Creek Park; Elizabeth races to reach her and brings her in bruised but alive. Oleg does not know why backup transport was ordered. Gaad waxes philosophical about his FBI career in flames as the Jennings kids drink beer with Stan's son. Philip is finally honest with Martha, over Elizabeth's objections. Martha knows that she will be completely alone in Moscow. Will tomorrow's plane carry one rat or two? Or will Martha bite the Valium bullet and refuse to be forced to defect and commit further treason?

The Jennings hit their breaking points as they try to handle their local agents such as Martha.

In the season 4 finale, Elizabeth & Philip race against the FBI to retrieve a mysterious package. Paige finally begins considering whether or not she would like to enter the family business.

Stan and Oleg wrestle with the harsh consequences of their complicated history, as Philip and Elizabeth face a new mission with devastating implications for their country.

Philip and Elizabeth have qualms about a new assignment, while a specter from Philip's past creates unforeseen dangers. At the FBI, Stan makes a shocking play that could throw his career into turmoil.