Gibbs sends Bishop and Quinn to Philadelphia to work with MI-6 Officer Clayton Reeves on the murder case of a British operative. Meanwhile, Quinn deals with the NCIS case that caused her to leave the field.
Two boys find the body of a Navy commander in a quiet suburban neighborhood; Gibbs and company investigate. EJ Barrett reappears from her hiatus but remains a target. Another man dies, and the gang protect EJ and find and catch the killer.
A Navy woman lieutenant commander dies of gunfire; she has served as a Naval attaché overseas, and her husband is a detective for the Metro PD; Gibbs and company investigate; the widower's help does not help, but the gang solve the puzzle.
At a diner an unknown person with a drawn pistol approaches Gibbs, who deals with him; then Gibbs experiences flashbacks and fantasies, which Franks explains. The next day McGee announces a decision, then the gang gear up and head out.
A civilian and a Navy captain die of gunfire in Washington, DC; Gibbs and company investigate; the Duck sees unusual undergarments, which are also costumes. The gang solve the puzzle and nab the bad guys; Wendy reveals something to Tony.
When two burglars enter a home in Arlington, Virginia, in the burbs of Washington, DC, they find the hanged body of a man; the victim proves to be that of a psychologist (with a PhD degree), who was also a Naval Reservist on active duty, and who held a high-level security clearance for his work, which included consulting with the US Department of Defense (DoD) on a psy-ops program; while Gibbs and company investigate, they soon encounter Dr. Rachel Cranston, who was a colleague of the victim, and with whom they've dealt before. Another mind-gamer shows up, and Abby ...
When Gibbs meets with a Navy chief petty officer and his attorney (to make a deal), the CPO collapses and dies; while the gang investigate, they find a connection to an illicit arms dealer. The team figure it out, and everything works out.
While Gibbs and Tony man a protective detail for the SecNav, a gunman shoots the secretary; the NCIS investigates quietly with the help of Dr. Ryan. Blackmail is involved; the gang and Ryan figure it out and find a hacker and the bad guy.
While on liberty in Baltimore, Maryland, a boatswain's mate second-class dies of a stab wound; Gibbs and company investigate; the prime suspect is a brother-in-law of Vance. The team persist, Abby solves the case, and they nab the bad guy.
A picnicking couple encounter a dead body, which proves to be that of a first lieutenant in the US Marine Corps; after Gibbs chats with Dr. Ryan, he and the team investigate; the gang see that the victim had plummeted from somewhere in the sky after he had first been beaten, stabbed, and shot; in one of his pockets they find a challenge coin, which they trace to a woman commander in the Navy Chaplain Corps, who is on duty with a relief team in Colombia. Ducky finds curious clues, and Abby interprets them (connecting to Colombia); Ziva communicates with Monique, a ...
A fire in a warehouse in Baltimore brings in the NCIS; while Gibbs and company investigate the fire and a death, they find connections to the Phantom Eight and the Watcher Fleet. The gang work with a city arson investigator. [Continued.]
Gibbs and company continue to investigate an explosion and a fire; Tony, McGee, and Ziva work aboard aircraft carriers; Ducky and Abby provide much support. Tony and Ziva nab a bad guy, who tells who hired him and why. [Continued.]
Dorneget gets a surprise from a dentist; Gibbs and company continue to investigate Dearing and the thermite incidents. Dearing visits the Navy Yard and messes with Gibbs. Moves and countermoves abound; Vance disappears. [Continued.]
Gibbs and the gang continue to pursue Dearing, the explosions, and the disappearance of the director; Dearing continues to mess with Gibbs and Ryan. After another explosion and another death, disaster strikes at the Navy Yard. [Continued.]
Abby has more nightmares; Navy Seabees continue to work on the building; a shrink does mandatory psychologic evaluations on all hands; the body of an armory worker appears four months after the explosion; Abby and the rest work out it all.
Ducky, on medical leave, unofficially calls for the exhumation of the body of a commander whose autopsy he conducted 12 years ago; he now suspects murder; the gang investigate another death, and they find the connection and the solution.
An inflatable raft washes ashore with three survivors from a missing Navy helo; the pilot also is missing; Gibbs and company plus Borin (of the CGCIS) investigate. The team and the other Abby find the pilot, the truth, and the chopper.
While the Gibbs team investigate a murder of a Navy petty officer first-class, Gibbs himself sees a Medal of Honor, which his father's former best friend received for valor during WW2. The gang figure out and work out both problems.
Two Marine officers return from Afghanistan after an ambush; one night one of them dies in a fistfight in an alley in Washington, DC; Gibbs and company investigate. The gang see a familiar face but do not yet find the person. [Continued.]
Gibbs tells Joe that Joe was right about Kersey's presence with the enemy in Afghanistan, and that he and the gang need his help to find the bad guy; Gibbs talks with Joe, his brother (Evan), and their father. Evan stays to help Joe, but their father goes back home in Ohio; Joe goes with Gibbs to see Paul, another member of the outfit, who responds negatively to Joe. Abby uses virtual-reality (VR) gear to help Joe recover some of his memories; the gang increase their efforts to find Kersey; Gibbs continues to work with Joe; they catch a clue; the gang find Kersey's ...
A kidnapper shoots to death a Navy captain who intervenes; the bad guys get one teenage girl but not the other; both girls are Navy juniors; Gibbs and company investigate, pursue, solve, capture, and recover. Tony joins Ziva and her date.
A Navy seaman fires on Fornell, who returns fire and kills him; Gibbs and company investigate, along with Fornell and the mutual ex-wife of Gibbs and Fornell. The gang find frozen fish, a dead body, a missing accountant, and two bad guys.
A Navy Lieutenant Commander returns from an overseas tour to her home and finds the decomposing body of her husband. When Gibbs and his team investigate, they find a new kind of uncirculated $100 bills.