A Navy petty officer (cryptologic technician first-class) dies of a single gunshot to the back in a park in Baltimore, Maryland; Gibbs and company investigate; at the scene both a clue and a man attract Tony's attention; Delilah joins the gang for this case. Abby shows Gibbs the victim's notebook computer and tells him about it; she also links Tony's clue (purple chewing gum) to the man whom Tony saw at the scene; Tony links that man, Anton, to one of his cases at the Baltimore PD, and he finds him again but loses him again. Gibbs and McGeek meet a headhunter, who provides missing answers, and who invites McNerd to call her. Tony goes to Anton's sister's pad, where he runs into Gibbs and McGee, and where the three of them find merchandise but no sister (because she has disappeared); later they find Anton elsewhere. Gibbs and Tony put the pieces together, find the bad guy and arrest him, and find the sister and return her to Anton. Tony finally gets some sleep.