Ari and Kate
27 episodes of NCIS carry this thread, 1d 3h in all — 5 of them are in The Essentials.
Arc membership is derived from each episode's own title and summary text. It shows where a thread is foregrounded, not every episode it touches.
In airing order
A Marine mysteriously drops dead aboard Air Force One and jurisdiction problems force Gibbs to share the investigation with a Secret Service agent.
A Marine dies when his parachute fails and he crashes through a car during a training exercise, and Gibbs suspects he was murdered.
The discovery of the body of a Navy submariner whose features are all but obliterated leads Gibbs to believe a terrorist has stolen the man's identity and is aboard a sub.
Gibbs and his team investigate when a dead Marine's wife receives a call from someone claiming to be her husband.
The discovery of a leg with a Marine tattoo on the calf leads the team to a small town where they uncover a murder scheme involving deception and greed.
The team investigates the murder of a Marine recruitment officer, who was killed, as the team discovers, by a highly skilled sniper.
The team investigates the murder of a Naval officer who was shot as he tried to help a stranded motorist.
The FBI asks Gibbs to find his former Marine C.O., who they've accused of stealing money from a mission in Iraq. But Gibbs is convinced that the man who trained him is innocent.
The NCIS agents search for a missing marine, who unbeknownst to them, is being tortured in a cell by a mysterious captor.
When a Marine is killed with a specialized military weapon, the agents investigate the illegal weapons market and find an undercover ATF agent (Bellamy Young) also working on the case, and Gibbs asks her to work with them to find the killer.
Gibbs' obsession with finding the terrorist Ari (Rudolf Martin) reaches its zenith, and is timed perfectly, as Ari is training men for an attack on Marine One with President Bush and Prime Minister Sharon on board.
The NCIS team is called in to investigate when a perfectly functioning Marine helicopter is found in the middle of a crop circle.
Body found on a Marine firing range leads the team to discover a Mafia dumping ground.
Gibbs and his team must clear the name of an elderly Marine who confesses to murdering his best friend nearly 60 years ago.
Gibbs and his team are called to the scene when a Marine's wife kills an intruder who tried to rape her.
The NCIS team investigates when a Marine records his own murder on video as he falls off a cliff.
Gibbs and the team head back to school when a Marine in an ROTC program is found murdered on a college campus.
Gibbs' worst fears are confirmed when he learns that his nemesis, Arab/Israeli double agent Ari (Rudolf Martin), is back in Washington D.C. on assignment to kill him. Ultimately, the NCIS team discovers that Ari has a bigger plot... and they end up paying the ultimate price trying to thwart it--the death of a team member.
While the NCIS team deals with Kate's death, Gibbs' determination to finally put an end to Ari's reign of terror mounts.
Ari continues to wreak havoc on the NCIS team as he uses its members as pawns in the game he is playing with Gibbs.
Gibbs and the team investigate the murder of Marine's wife that appears to have been broadcast over the Internet.
Gibbs and the team investigate the murder of a supermodel filming a reality TV show on a Marine base.
When the wives of two Marines are murdered, Gibbs and the team are called in to investigate.
Gibbs and the NCIS team make a disturbing discovery when they bust an illegal automotive chop shop run by Marines.
The team investigates the mysterious explosion of an ambulance that is supposedly carrying the remains of a Marine killed in a car crash.
Gibbs and the team are called to investigate when a group of teens on a nature hike discover Marine dog tags in a national forest.
Gibbs and the team are called in when a couple of kids stumble upon the body of a missing Marine in a frozen lake.