A decomposed body is discovered in a tub of acid at a naval base and Ducky and Abby learn that the victim was a submariner. Gibbs discovers that there have been no reports of a sub crewmember missing, so he deduces that one of the subs has an imposter on board. With this new information, the team must find out which sub the man posing as the victim is in and what intentions he may have towards the sub.
Elenco: David McCallum , Mark Harmon , Sean Murray , Pauley Perrette , Brian Dietzen , Michael Weatherly , Rocky Carroll , Cote de Pablo , Emily Wickersham , Wilmer Valderrama , Maria Bello , Duane Henry , Sasha Alexander , Jennifer Esposito , Tim Kelleher , Diona Reasonover .