When a ransomware attempt causes a dam to malfunction, Ernie and a team of hackers are tasked to find the culprit quickly, before all power and water is cut off on the island. Also, Lucy and Whistler work together, giving Whistler a chance to apologize to Lucy and mend their relationship.

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 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.

After a brazen daytime robbery of a Navy Federal Credit Union, the NCIS team tracks down a group of adrenaline-seeking thieves. Meanwhile, Tennant grows suspicious of Sam Hanna's reasons for being in Hawai'i.

Following a devastating ambush with a deadly bioweapon, the NCIS team must track down a mysterious terrorist group before they can strike again.