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 finds Isaac Johnson in Texas after an attempt on his life. Nadine discovers just how much influence Patricia Gregson wields, and a traumatized Julie fights to stay strong for her family.

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.

Bob Lee works to piece together Solotov's motive for targeting their unit. Nadine uncovers a surprise witness to the event that set everything off. Solotov's hunt has him hiding in plain sight.

Bob Lee tracks Solotov's money, pitting himself against a Mexican cartel. Nadine helps a journalist investigate a cover-up involving Bob Lee's unit. Julie makes her frustration heard with a gun.

Bob Lee and Isaac must team up to escape a Mexican prison before Solotov finds them. As Nadine digs deeper into Atlas, the cover-up points back to Bob Lee's unit. Julie has problems with the law.

Bob Lee tries to draw out Solotov, but realizes he holds the upper hand; flashbacks reveal the origin of Solotov; Isaac is courted by his creator. Season Finale.