While two brothers play on a frozen pond, one of them sees the body of a man below the surface; Gibbs and company investigate, and they find three more such bodies. The first body is that of a Marine first sergeant, missing four months, and the other three are of members of a Latino gang; all four men died of gunshot wounds, not of drowning. One question asks whether the Marine was on a personal mission to avenge the accidental killing of a private first-class from the same company a year before. Abby provides answers, as always. The team figure out an internal power struggle within the local gang. Gibbs plays two factions against each other and allows them to sort it out themselves.
—DocRushing