While on vacation with his friends, a teenager while swimming finds the body of a young Naval Seaman wearing dress whites as well an officer's ceremonial sword and chains around his waist. The NCIS team then head to the USS Foster to investigate and during the investigation, discover some disturbing secrets about the victim as well as evidence of a potential and devastating biological attack against the Foster that puts the lives of its crew and also those of the NCIS team in grave danger...