When a figure from Tennant's CIA past re-emerges, the NCIS team seeks help from the most unlikely place to catch a killer who threatens to destroy everything Tennant has built.

The discovery of a dead former MI6 agent uncovers secrets from Tennant's past, forcing her to go to extreme lengths to track down the responsible party.

When Lucy receives a strange call on night watch from a man admitting to murder, the NCIS team sets out to find him.

After the mysterious death of an astronaut in a highly sensitive Mars simulation, the NCIS team must send Ernie into the habitat to investigate alone.

When Tennant interrogates a suspect during his helicopter transfer and the helicopter crashes, she must utilize her skills to save herself and the other passengers.

Captain Milius returns to Hawai'i as the NCIS team works to catch a dangerous high-value U.S. Government target with the help of an informant unlike any they've ever encountered. Also, Tennant and Daniel deal with Alex's acceptance into the Naval Academy.

When Navy residents discover their vehicles were burglarized overnight, the NCIS team connects it to a series of peculiar crimes and tracks down an unlikely bandit. Also, Whistler struggles with an uncooperative CI and Alex weighs his college options.

When a Navy deserter accidentally comes out of hiding, his family becomes a target that drives the NCIS team and Charlie 1 to investigate who is after them. Meanwhile, Lucy surprises the team by returning to Hawai'i from her agent afloat job early.

When the murder of a captain and his wife echoes a previous case, the NCIS team brings in a former team member to help determine if they are dealing with a copycat killer.

Following a close call at a meth lab explosion, the NCIS team learns Kai is being targeted by his old friend-turned-criminal and must take him down. Meanwhile, Lucy gets her first big case aboard her aircraft carrier.

When an elite special forces Marine captain is murdered, the NCIS team finds a suspect in a really unusual place.

When Special Agent Pike is ambushed while working undercover with a local Japanese crime family, the team must find the person responsible for orchestrating the attacks. Also, Kai goes deeper into his investigation regarding an old friend turned criminal.

Tennant, Jimmy Palmer and Sam Hanna find themselves captured by a woman claiming to be a CIA agent demanding intel from the team. Also, Jesse, Ernie, Whistler and Alden Parker learn about an asset that arrived in Hawai'i who could be connected to several overseas assassinations.

When Commander Chase is abducted from her home by an Army Ranger accused of murder, the NCIS team must act quickly to find her and the suspect.

When a naval officer is murdered while moonlighting in community theater, the NCIS team recruits a familiar face to help lead them to a ruthless international killer. Also, Kai enlists Whistler to open an investigation into an old friend turned criminal.

When the mother of a young boy goes missing, the NCIS team sets out to find her and learns they aren't the only ones searching for her.

When a Marine Corporal dies in a tide pool after being exposed to fentanyl, the NCIS team must quickly find the source of the drugs. Also, Alex talks to his parents about taking a gap year and Ernie reveals personal news to Lucy.

The NCIS team investigates the death of a Navy sailor and goes head-to-head with a ruthless local criminal organization. Also, Lucy looks for a new apartment.

When a Navy sailor washes up dead in a sacred, forbidden kapu site, the NCIS team brings CGIS Special Agent Pike to unmask the mystery and catch a possible serial killer on the island. Also, Tennant meets Alex's new girlfriend.

Tennant and the NCIS team suspect foul play when they investigate a fatal car crash involving a Navy officer who turns out to be an imposter. Also, Whistler finds herself in danger when she goes undercover to learn the truth behind the accident.

The NCIS team's investigation takes them deep into the world of illegal street racing after a Marine staff sergeant's body is discovered in a junkyard. Also, Tennant is concerned Alex is hiding something from her, and Whistler is anxious about introducing Lucy to her co-workers.

Special Agent Tennant's team, along with NCIS agents Nick Torres and Jessica Knight, learns about plans for an attack on RIMPAC (The Rim of the Pacific Exercises) in Oahu, the world's largest international maritime warfare exercise.