A body is found at an unmanned aerial vehicle testing site. Palmer vents because he's doing the work of two medical examiners. McGee suggests he hire his own assistant. McGee identifies the body of Daniel Backer, a retired gunnery sergeant. He was dead before the missile hit. Palmer said the body had been moved after death. Backer worked on the missile project. Marine Diana Murphy, Backer's ex-girlfriend who fired the missile against orders, has disappeared. Palmer auditions assistants. Backer's cause of death was a gunshot wound. The M.P.s found Murphy at Backer's place. Gibbs determines that Murphy is deaf. An top-secret research accident that Murphy and Backer were involved with caused her hearing loss. Murphy didn't have the opportunity to kill Backer. Backer accidentally shot Murphy with an experimental sonic weapon. They hid her hearing loss as best they could. Murphy said Backer didn't get along with her step-brother, Ronald Kepczak. He said Backer suddenly cut him off from his recording studio. Kasie is trying to identify the metal in a bullet Palmer found in Backer. Torres and McGee find stolen sonic weapons in Backer's studio. Christopher Crane, a young British candidate, acts just like a young Ducky. Murphy has been medically discharged. Backer falsified Murphy's signature on the inventory form that helped him steal the weapons. Backer told her that he was going to meet someone on the night they fought. Backer gave the weapon to Professor Zahir Najjar for testing, to see how well it worked. He was a whisteblower but his reports were buried. Company owner Edison Geary admits to burying the reports but he was working the night of the murder. He is selling his stake to chief developer George Ingram. Ingram is at Murphy's apartment. He attacks her but she takes him down.