Two Navy sailors, both of whom are serving on the USS Enterprise overdose on meth, prompting the NCIS team to investigate. When they arrive on the ship to investigate further, both sailors insist that they've never touched the drug despite their tests clearly saying otherwise. With the help of the Agent Afloat and who once worked for Gibbs, NCIS dig deeper to get to the truth but things change when the first sailor dies under mysterious circumstances, the case is later upgraded to a murder investigation with Gibbs believing that a senior officer on the ship is knowingly jeopardizing the lives of his crew by secretly giving them performance-enhancing drugs...