Sam's former contact and "brother" Moe is attacked in prison.
The team discovers that Moe was beaten as an initiation into a terrorist group that has members in the prison. NCIS told Moe if he got close to the leader of the group they would get him out of prison.
Sam comes back to the team with this info and Hetty surprises them all when they find out Nate is already placed in the prison watching Moe.
Sam also goes undercover to get close to the prison's group leader and find out what the group is planning and to protect Moe.
The group was working with a prison guard to create an escape plan to get the terror group leader's brother, Abdul Habaza, and his lieutenants out of prison and back to Yemen.
Sam and Moe know they must help Abdul escape in order for them to track him, using overwatch, and gain intelligence on this organization.
The assistant warden is dirty and is about to expose Sam, Nate or Moe to Abdul so they must put the plan into action now.
Moe assists the team in the escape but pays the ultimate price when Abdul tortures and kills him for information on the undercover agents. Moe covers for Sam, who is determined to avenge him someday.
Meanwhile, Callen gets a clue to his past and Hetty allows him to leave to pursue it.