While on liberty in Baltimore, Maryland, a boatswain's mate second-class dies of a stab wound; Gibbs and company investigate; the prime suspect is a brother-in-law of Vance. The team persist, Abby solves the case, and they nab the bad guy.

When a marine is killed, the team investigate. They learn the man worked at a Center that helps Afghan immigrants. They go there and learn the man had a heated discussion with an Afghan. They learn the marine worked with his father when he was stationed there and he tried to get his family out but his parents were killed by the Taliban. They think he blamed him for their deaths. They try to talk to him but he runs. They learn he has bomb making materials. They eventually apprehend him and he tells them the marine was trying to help because someone was forcing him to make the bomb only he doesn't know. So they need to find out who and what they want the bomb for. Palmer is concerned about his daughter going on a date.