A decomposed body is discovered in a tub of acid at a naval base and Ducky and Abby learn that the victim was a submariner. Gibbs discovers that there have been no reports of a sub crewmember missing, so he deduces that one of the subs has an imposter on board. With this new information, the team must find out which sub the man posing as the victim is in and what intentions he may have towards the sub.

Bishop is more determined than ever to seek revenge for the murder of Qasim, her late boyfriend, after Gibbs and the team find a new lead in the Chen case. Also, Torres teaches the agents the art of pickpocketing.

Gibbs and Ducky are watching TV when they see the host handling a 200-year-old war stick that could be a match from a decade-old cold case.

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.

While Gibbs attends the memorial service for a friend who was lost at sea, he discovers that the deceased, Navy Captain Phillip Brooks, has been hiding in a fallout shelter after his boat was attacked and he swam to shore.

After a 50-year-old tape recording left by a murder victim is found, the NCIS team tries to exonerate Ray Jennings, the Marine serving a life sentence for the crime.

The team’s holiday plans are put on hold when the murder investigation of a Navy veteran includes the discovery of a newborn baby who has no identification and no apparent ties to a family.

The NCIS team investigates a man overboard fatality from a Navy destroyer at sea. Also, Torres is frustrated with Vance’s assignment to mentor three high school students.

NCIS investigates the murder of a Marine Major believed to have been killed in the 9/11 attack on the Pentagon after human remains are discovered at a construction site. A personal history with the victim drives Gibbs to solve her crime.

The NCIS team links a bizarre crime scene at Arlington National Cemetery to a string of attacks on homeless veterans. Also, Vance orders McGee, Bishop and Torres to complete hours of evidence garage cleanup duty for withholding information.

The NCIS team investigates the murder of a musician in the Navy’s most elite band that performs at diplomatic events around the world.

The lead suspect in an NCIS murder investigation is a woman Gibbs' friend, Phillip Brooks, met on a dating site. Also, Sloane has a secret admirer on Valentine's Day.

As the NCIS team investigates the death of a Navy officer murdered the same way as his parents a decade ago, they stumble across a storage container filled with dollhouses that display recreations of murder scenes. The team agrees to clean out their living spaces, but some have a harder time saying goodbye to their possessions than others.

Gibbs and Fornell attempt to track down the leader of a drug ring who supplied drugs to Fornell's daughter. Also, the team deals with the case of a missing cadaver from the NCIS autopsy room.

NCIS dives into the competitive world of food trucks after finding a man frozen to death in the back of one.

When members of an NCIS Regional Enforcement Action Capabilities Training Team (REACT) are killed during an explosion, NCIS Special Agent Jessica Knight (Katrina Law), the lone surviving member, helps crack the case using high tech body armor.

As the NCIS team searches for Gibbs after wreckage from his boat is discovered, they find out he was tracking a serial killer with journalist Marcie Warren, who wrote an exposé on him.

NCIS investigates the death of a man on a cruise ship whose body is discovered in the ship's sauna by none other than McGee's mother-in-law, Judy.

As NCIS investigates the cause of death of a reservist Navy SEAL surgeon, they're forced to bring Vance's daughter to help with a highly dangerous mission.

NCIS investigates the apparent suicide of a retired Navy officer who was in Palmer and Knight's grief group; Torres gets a call from NCIS Special Agent Jane Tennant to come to Hawai'i.

The crossover continues on NCIS: Hawai'i S01E18 T'N'T (II).

NCIS investigates a ring of clever teenage partygoers when a string of break-ins takes place at Marine Base Quantico. While working the case, Special Agent McGee forms a bond with one of the teens, Teagan Fields.

McGee’s personal life and professional life intersect when a dad from his children’s school is linked to a break-in at a government storage bunker.

NCIS agents from Washington, D.C., Los Angeles and Hawai’i, all in D.C. to attend the retirement party of a beloved Federal Law Enforcement Training Center (FLETC) professor, find themselves jointly investigating his shocking suicide.

The crossover continues on NCIS: Hawai'i S02E10 Deep Fake (II) and NCIS: Los Angeles S14E10 A Long Time Coming (III).

In preparation for a role, a world-renowned actress shadows the NCIS team as they investigate a decapitation case.

The NCIS team digs deep to investigate a Navy lieutenant who’s accused of trying to murder her husband but has no memory of the attack. Also, Kasie navigates a potential medical scare.

As NCIS mourns the loss of Ducky, the agents find comfort in working on one of his unfinished cases involving a woman whose father was dishonorably discharged from the Marines.