A New Jersey couple is shot in their backyard, where investigators find a fallout shelter with items that lead the Agency to suspect that the husband was a Russian spy with a nuclear that may now be on the black market.
When the Agency learns that someone has in their possession anthrax, they try to find out who and how they plan to use it. They think they found the man, a man named Zimmer. They discover he tried to make contact with someone he knew years ago who is now a housewife. So they arrest her and try to get her to tell them what she knows which she claims is not much. They also try to intercept the anthrax which is on it's way.
Matt discovers the truth about the death of his brother Eric in 1999 while on assignment in Kosovo. In the meantime, Haisley heads to India to work with a double agent who has inside information on the nuclear-weapons program.
When a newspaper article reveals that a high ranking KGB man worked for the U.S. during the cold war. The man fearing what will happen if he's exposed alerts the C.I.A. Pierce who was his handler must try to find a way to protect the man especially since a KGB man who likes to weed out traitors, is close to finding out who the "one" is.
When the son of a British official is kidnapped, and it's believed that it's so that the official could be coerced into giving up information. So Quinn sends Carl and Matt to England to see what they can do to help.
Matt trails a terrorist entering America from Mexico the Agency suspects is a suicide bomber, but his exact target is unknown. In the meantime, Haisley becomes attracted to a translator working the case.
Haisley's life in danger when he takes the place of an agent dealing with the Russian mob after the agent realizes his contact already knows him and Gage must decide whether to let Haisley go on with the mission.