When an accounting office of the DOD is attacked, the team investigates because the office is responsible for among things is the budget of special ops like theirs, which means whoever was behind the attack may have info on various ops. Eventually they learn that one of the people working there evaded them and was seen entering Mexico. So Sam and Callen are sent to find him. When they arrive, DEA agents relieve them of their weapons, credentials and cellphones because they were not given permission by the Mexican government. They track the man to a brothel but he's not there. The girl whom he was with, takes them to see him and he's afraid thinking that they're among the ones who attacked the office. When he tells them why he thinks they were attacked, the men who attacked the office show up and demand him and Callen and Sam don't have weapons that are a match for what they have.