Trying to make an undercover gun buy, NCIS is soon involved in a firefight with arms dealers. Bishop shoots two of them while sliding across the floor, but their leader escapes. Marcie discovers a pattern for the serial killer they're investigating. GIbbs finishes his boat. Marcie couldn't find the latest body to fit her pattern. Gibbs suggests checking missing persons. The team tracks the dealer to a stash house. They discover that he is selling classified secrets as well as weapons. Jessica offers to make calls to the NSA about the file they found. Kasie brings a bug detector to Gibbs. GIbbs sweeps Marcie's home for bugs after finding one in his basement. He finds one in a plant. They pretend to stop investigating. The NSA thinks Bishop originally leaked the file they found. The dead men ate an obscure Chinese fruit before they died. Bishop visits Gibbs and tells him she's angry at him. She realizes that he doesn't plan to return. Jessica offers to help the shorthanded team. Bishop tells Vance she leaked the file and quit. McGee confronts Bishop. He wonders what else they don't know about her. Marcie refuses to back off the investigation. Gibbs says the police searched the wrong area for the body. Kasie finds the arms dealer who ordered Chinese takeout. Gibbs informs McGee that Bishop is at a crossroads and that no one can help her. Torres and Jessica use takeout food to capture the arms dealer Murati. Jessica joins McGee to interrogate Murati. He knows nothing about the file although he admits to everything else. Gibbs explains Rule 91 to Bishop: "When you decide to walk away, don't look back." Torres tracked Bishop to Odette's house. Odette planted the file. Ellie kisses Nick goodbye. Gibbs' boat explodes but he swims away.