Bob Lee Swagger and wife Julie join his former Marine unit in Germany and narrowly escape a deadly terrorist attack. FBI Agent Nadine Memphis, meanwhile, takes a job in Washington with Patricia Gregson.

Bob Lee investigates the terrorist attack that may have targeted his Marine unit. Memphis helps on the ground in Germany. Flashbacks to Afghanistan help shed light on who might be after them.

Bob Lee and Isaac learn the world's greatest assassin is in the U.S. Flashbacks to a mission in Afghanistan reveal his identity: Solotov. Nadine comes to Texas with suspicions of a conspiracy.