In Washington DC, a petty officer's body is found four and a half months after he had died; another officer dies in Morocco and Ziva sustains an injury. Gibbs and company find a link and reach a solution. Ziva gladly returns to the NCIS.

Gibbs and company start looking into the murder of a Marine. Gibbs and McGee go to Los Angeles for a joint gig with the NCIS Office of Special Projects in LA due to a suspected link. The investigation continues on both coasts. [Continued.]

Ziva finds Tony and Michael on a floor; Michael dies soon afterward; the next morning her pad explodes. McGee and Abby find answers. Vance, Gibbs, Tony, and Ziva go to Tel Aviv; Ziva remains, and the others return; Ziva runs into trouble.

The body of a UA Marine, last aboard a ship with Ziva, turns up in a shrimping net in the Indian Ocean. Vance flags Ziva's application while he questions her. Mossad and more bodies appear. Ziva and Abby tell all. Gibbs puts Ziva to work.

Vance hosts a conference of high-level members of the NCIS; he invites Eli, who accepts. Eli's presence raises security concerns; Gibbs and company take part in the protective arrangements. Threats arise, and the gang respond. [Continued.]

An attack has killed one and left Vance with serious injuries; Gibbs takes charge by Vance's order. Eli reveals details about an operation 22 years old. Gibbs and the gang put the pieces together. The bad guy emerges, and justice prevails.

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.

After the attack on NCIS, the President orders all agencies to pursue Harper Dearing with "extreme prejudice". Meanwhile, Ducky tries to recover from his heart attack.

A human ear in the Potomac River leads to the rest of the body, wearing a uniform of a Navy petty officer; Gibbs and company investigate. Ziva's father shows up, as does his Iranian counterpart. Gunfire interrupts a dinner. [Continued.]

A lance corporal collapses and dies on an obstacle course at the MCB, Quantico, Virginia; Gibbs and company investigate; Ducky sees many wounds. Another injured Marine dies. The team figure it out. Vance finds and solves personal business.