A group of teenage boys at play find the body of a Marine impaled on the stump of an old fencepost; Gibbs and company investigate; however, Ducky says that the hole through the torso had resulted from something else, and that one or more other people placed the body onto the post. The victim was a staff sergeant and an armorer at the Marine Base at Quantico. The gang determines that the penetrating wound resulted from a warhead from a shoulder-launched assault weapon; they look into the black market for illicit high-power weapons from military sources; they meet an ATF special agent, who takes part in an unusual way. Gibbs and the others solve both the murder and the diversion of the weapons.
—DocRushing