Inside a drum of hydrofluoric acid at an industrial site aboard the Naval Station, Norfolk, Virginia, two civilian workers find the decomposing body of a man, apparently a submariner, who died after a blunt instrument fractured his skull. Gibbs and his team go to Norfolk to investigate; attention concentrates on one particular submarine and a theft of identity; Gibbs and Kate continue to USS Philadelphia (SSN-690), which got underway the day before. The commanding officer and his chief of the boat give limited and begrudging cooperation due to the nature of the exercise in progress. The other members ashore help greatly; Gibbs nails a terrorist aboard and saves the crew from mass death.
—DocRushing