When Angie is put in a dangerous situation, she can only leave him one clue as to what has happened to her. JT must recall his old Special Ops missions in order to find the answer.

JT and a SO team are sent to Detroit to address a situation with a radical Christian group that has taken over a mosque and taken hostages. Sonny must address legal concerns around the action due to FBI jurisdiction and the Posse Comitatus act.

McNulty discovers that a captured Navy Seal could be alive and he and JT are set to save the man. However, they soon face resistance from the Pentagon and might have to do what is known as a "backdoor" mission to save the soldier. Also, more about McNulty's mysterious past is revealed during this endeavor.

On Christmas Eve, JT works on a humanitarian aid mission for an Afghanistan village that helped Delta several years ago. He finds the village confronting bad weather and an advancing Taliban force. Also, Sonny helps JT's father who needs a favor.