Stan is an FBI counter-intelligence agent and moves to Northern Virginia with his wife, Sandra (Susan Misner) and his son, Matthew (Daniel Flaherty) across the street from Elizabeth (Keri Russell) and Philip Jennings (Matthew Rhys). Stan is unaware of the fact that Philip and Elizabeth are undercover KGB agents but becomes suspicious when he learns that a car similar to Philip's is seen near the site of Timoshev's, a Soviet defector, abduction but finds nothing when he covertly inspects Philip's trunk.
In the second episode, Stan blackmails Nina Sergeevna (Annet Mahendru), a Soviet embassy clerk, to spy for the FBI. Nina feeds Stan information about a Soviet agent who was killed the night Timochev went missing. As Stan gets to know Nina, he subsequently grows further apart from Sandra from how much he works and isn't home to spend family time together. After Stan misses a family dinner due to work, a co-worker takes him to a bar and tells him to pick out a woman to have casual sex with. Stan calls Nina instead and they sleep together but the way Nina conducts herself leads him to believe that she is using Stan and may be a double agent. She is tasked to try and turn Stan but starts to fall in love with him instead. Agent Frank Gaad (Richard Thomas) is Stan's FBI supervisor, gives him the keys to a safe house and tells him to take Nina there which then becomes their "love nest".
On Stan's unauthorized initiative, the FBI seize Arkady's assistant Vlad which course of events lead Stan to return to the safe house and kill Vlad. When Nina asks about Vlad's death, Stan lies and promises her he will find out who killed him. When he gets home, Sandra asks him to quit the FBI and move away with his family. When he says no, she leaves him. He goes to Nina and attempts to end their affair, but ends up losing his resolve and sleeps with her instead. Nina doesn't trust what Stan is telling her about Vlad's death and after she gets promoted, she is given access to the material obtained by the Weinberger bug. She keeps the information from Stan in order to further investigate Vlad's death. Stan and Gaad continue to look for a thirty-something married couple and produce a sketch of them while Nina is sworn into Directorate S and, after a conversation with Stan, confesses her spying to Arkady and offers to become a re-doubled agent. Stan tells both Sandra and Nina that his mission will soon be over but Sandra rebuffs his attempt at reconciliation and Nina tells Arkady, who has accepted her offer in spite of Moscow's skepticism.
Nina informs Stan of a new arrival at the Rezidentura, Oleg Igorevich (Costa Ronin). Stan follows Oleg one night only to have Oleg misleads him to a port where he tells Stan that he's the only one who knows about Nina and threatens to expose her. Stan asks Nina to take a polygraph test if she wants to get exfiltrated. Arkady forces Stan's hand to steal the "Echo" program in exchange for Nina's safety. When Oleg pressures Stan more, Stan gives a surveillance log to Oleg and later promises to protect Nina. He drops a package at the agreed location, but it turns out to be only a note that says "Tell Nina I'm sorry". A heartbroken Nina goes to leave the Rezidentura to return to Moscow to stand trial for treason while Stan sadly watches her leave from a parked car.
Gaad also informs Stan that Nina has been charged with espionage and treason. He tries again to reconcile with Sandra, trying to understand the EST she's been going to, so he goes and asks Philip to go too. Stan finds the training ridiculous and useless, much to Sandra's annoyance.