Capt. Milius continues to work with Tennant and her team in the aftermath of the prisoner exchange between U.S. and Eastern Europe; Whistler takes Ernie's advice and makes a grand gesture in hopes of winning back Lucy.

Capt. Milius returns to Hawaii for a secret prisoner exchange operation, and brings in Jane to be his personal security escort in the Philippines, where the exchange will take place.

When a Navy seaman is involved in a murder, the team is called upon to work the case on its day off; Lucy finds out Whistler turned down a promotion in Washington to stay in Hawaii.

The team investigates a shipwreck carrying exotic animals that now threaten the native wildlife on Oahu; Alex sustains a career-ending injury; Kai asks a fish and wildlife agent out on a date.

NCIS agents Nick Torres and Jessica Knight travel to Hawai'i when they learn a key witness in one of their old cases has turned up there with crucial evidence.

After a ransomware attempt causes a dam to malfunction, Ernie and a team of hackers are tasked to find the culprit before all power and water is cut off on the island; Whistler gets a chance to apologize to Lucy and mend their relationship.

Kai goes under cover as a chef in a local restaurant to gather intel on a notorious criminal kingpin who has a connection to the eatery; Jane discovers that a school on the mainland has recruited Alex on a baseball scholarship.

As Jesse enjoys a day sailing with his daughter, pirates suddenly seize their yacht; the team must quickly locate and rescue Jesse's daughter.

While Jane is questioned following Maggie Shaw's arrest, the rest of the team investigates a mysterious case of Marines with damaged ear canals from a weapon that emits ultrasonic waves; Ernie visits his friend Dr. Tony Lee.

While Jane investigates Maggie's kidnapping, she's shocked when she learns the truth and enlists her team and Whistler to prove her findings.

NCIS investigates the mysterious death of a Navy engineer; Jane's mentor and friend is kidnapped; a New Zealand intelligence service case officer arrives and connects the Navy engineer's death to a Chinese black operation secret agent.

When evidence to put away a drug kingpin is stolen, Lucy goes under cover at an underground poker tournament to find out which high-roller is behind the crime; Lucy's feelings are in turmoil when Whistler's ex-girlfriend arrives in town.

NCIS crosses paths with Whistler's team while investigating a shipping container filled with contraband weapons; Tennant debates arresting Alex's friend's dad, knowing it will cause her friend to move away.

The NCIS team investigates a cold case involving WWII-era bones on the 80th anniversary of the Pearl Harbor bombings, and are shocked to learn they belong to a 100-year-old survivor of the attack.

When an anti-capitalist protester is murdered, Jane and the team investigate and find themselves caught in a war between eco-activists and a tech billionaire fighting over a piece of land; Jane and Capt. Joe go on a date.

When a Navy petty officer is murdered, Jane and the team investigate while protecting the victim's friend and colleague.

When Tennant and NCIS are tasked with finding a kidnapped social media star, they find that she is not who her husband, or her followers, think she is; the team is at odds with Whistler, who has an agenda of her own.

When a Japanese sailor is killed on American soil, evidence links the case to the previous murder of the victim's girlfriend back in Japan; Capt. Milius makes a personal request to Tennant.

When a beloved Hawaiian cowboy is shot while out riding his horse, Jane and her team must gain the trust of the Paniolo community to help find the culprits and protect the cowboy's life; Kai tries to convince his stubborn father to see a doctor.

Kai goes under cover with one of Hawaii's oldest surf gangs when a petty officer is murdered.

Tennant and NCIS must take down a notorious team of international thieves before they complete their final big job and disappear; Kai searches for a new place to live; Lucy and Whistler have a standoff about their previous encounter.