A Navy chief petty officer, Frank, dies of a slashed throat in his home; he worked with a highly classified technology with applications to submarines; Callen and company investigate. Frank's wife split and took their baby a month ago. Frank also worked with submarine technology before he enlisted; his patents in that field made him financially secure. From Washington, DC, Director Vance sends Abby, the punk-gothic lab techie, who has a unique theory that Frank was a victim of a serial killer, whom Abby calls The Phantom. G and Sam find the widow and her boyfriend, the latter of whom takes a short bike ride. Abby and Eric click, they go out on a date, and she disappears. G, Sam, and Kensi go undercover and put on quite a show; Eric sees Abby on video, then G and Sam see her in person; Sam mans a fire hose, and G zaps The Phantom. Abby solves 15 murders in as many hours; she next reports to Gibbs and McGee, who're on their way to rescue her.