An old skeleton comes to light; Gibbs sends McGee to question a prisoner convicted of murder in two identical cases; while he does so, other inmates kill a guard, seize McGee, and take over. McGee successfully negotiates and investigates.
On a sidewalk a former fiancée fatally stabs a petty officer; while Gibbs and company investigate, a different woman accuses Ducky of a war crime and stabs him through one hand. Ducky surrenders, but Gibbs sorts it out and gets Ducky free.
Two kids find the disemboweled body of a missing Navy captain; Gibbs and company investigate; Ducky finds a pentagram impressed into the victim's back. Another man dies. The team put the pieces together, and Gibbs and Tony nab the bad guy.
The Metro PD finds the body of an 18-young-old Marine who had grown up in the same hood where he died; the Gibbs team investigate with the help of Franks. They slowly assemble the picture, then a gentle social worker offers the last piece.
A man, impersonating Tony, dumps the body of a witness against him in a trial during which the impostor became convicted and imprisoned as a result of one of Tony's investigations; Tony and the gang sort out some of it but not all of it.
An agent of the NCIS dies in an execution-style shooting; Gibbs and company investigate. A radioactive painting provides clues, and an impostor federal agent causes trouble, but Gibbs and Tony, on horseback, and the others break the case.
Vance, using members of the Gibbs team, in Chicago works the case of the murder of a man who, Vance insists, was once a member of the Marine Corps. Gibbs wonders whether Vance has exceeded his authority. Later Vance hears what happened.
In Navy base housing in Norfolk, Virginia, a mother finds a pistol among the personal stuff of her 12-year-old son; Gibbs and company find a trail of old crimes and two recent deaths. The gang put the pieces together and find the shooters.
Kort dishonestly gets help from Gibbs and his team in neutralizing an international mobster who "has returned to the US". The bad guy's CPA, who launders his dirty money, enters the picture. Deaths abound, and the gang figure it out.
Local cops find the body of an enlisted Marine on UA; Gibbs and company investigate. The FBI haul Abby to a classified lab to replace a missing man, who was a target of the dead Marine. The gang figure it out and tie up the loose ends.
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.]
Gibbs and McGee continue with the OSP in LA. Rifkin shows up and interferes with the NCIS investigation. Two sleepers in a terrorist cell die, but OSP agents swarm a shop and grab others. Gibbs intercepts Rifkin and tells him to go home.
During a poker game at the home of the SecNav, an ICE agent dies while on the protection detail; Gibbs and company investigate with support from the FBI and ICE. An invisible man becomes visible and dead. Tony arrests Michael, who resists.
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.
Having not heard from Ziva anything, Gibbs, Tony, McGee, and Abby wonder; each starts sniffing and digging; they trace her to Somalia. Gibbs, Tony, and McGee go there; Tony and McGee become caught; Gibbs springs them all; they all go home.
Three men die during what they called a bachelor party; one was a Marine staff sergeant; Gibbs and company investigate. The clues lead to a cop, who later dies. The gang find the pieces and put them together; Ziva rejoins the team.
A critic of the NCIS has severely complained about an alleged cover-up of the death of a Naval officer; the griper falls to his death; both the NCIS and the Metro PD investigate; the Gibbs team figure it out. Ziva seeks Gibbs's signature.
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.
A Marine, a practical joker, dies, apparently by suicide by carbon monoxide; Gibbs and company investigate; Ducky rules out suicide, and Abby confirms. Tony starts to arrest the widow, but Gibbs stops him. The gang put the pieces together.
Gibbs's boat, which he gave to Franks, drifts, with two bodies aboard, into the Naval Station at San Diego. Vance and the team investigate. Franks and two relatives show up at Gibbs's house. The gang solve the case and make an arrest.
Two runners at the US Naval Academy find an unattended car and the body of a civilian physician; Gibbs and company investigate; Vance recognizes the MO of a North Korean woman assassin. The gang find the pieces, and everything works out.
A woman Naval officer dies during a break-in at an ISP facility in or near Washington, DC, then electric power goes down throughout the entire metro area; Gibbs and company investigate in the dark; they solve the case and grab the bad guy.
Jack visits Leroy for a special reason. Meanwhile a couple find the body of a Marine first lieutenant, barefoot and thinly clothed, on a prayer rug in freezing weather in a park; Gibbs and company find the pieces and elicit a confession.