A Navy lieutenant, otherwise in perfect health, dies under mysterious circumstances; Gibbs and company investigate; the vic's sister disappears; a long-time friend of the siblings recently died. The gang figure it out and bust the killer.

The body of a Marine corporal, minus his feet, shows up in the trunk of a junked car; Gibbs and company investigate. Abby and McGee go to Mexico on business; Abby returns with concerns. The gang figure out who killed the Marine and others.

The body of an NCIS agent turns up in a bonfire on a beach near the US Naval Academy after celebrations just before graduation; Gibbs and company learn also about a rape of a sailor, and Gibbs goes to see Franks in Mexico. [Continued.]

Gibbs meets Paloma, the head of the Reynosa drug cartel in Mexico; he gets a ride to Washington, where he talks with Vance in code. Tony and Ziva arrest a bad guy, who then dies. Ziva attends a ceremony. Paloma meets Jackson. [Continued.]

Gibbs must take desperate measures to protect his loved ones with Paloma Reynosa still on the loose.

Someone shoots and kills the executive officer (XO) of a Naval vessel, a commander, in his own stateroom; Gibbs and company investigate. However, a shrink (a persistent and presumptuous one) arrives to conduct mandatory psychologic evaluations for all members of the gang, and she accompanies them aboard the ship. Ziva recognizes the spent brass as Russian. Word of the murder spreads fast, for seven international journalists are aboard as guests; one reporter makes a confession and reveals a potential powder keg. The team continue, and they eventually find the solution. Meanwhile, the shrink also continues, eliciting a number of flashbacks, mostly related to Kate Todd, a former member and special agent. Eventually Tony and Gibbs realize who the shrink is, then she submits her report to the director.

The team must investigate a prison escape without Gibbs as he heads to Stillwater after his father's death.

When evidence reveals an NCIS team member is a hitman's latest target, the team must search through old case files to determine who is seeking vengeance.