Magnum is undercover as Santa and Higgins as his elf. They're staking out Barry, a bail jumper, for a case. They take him down after a brief chase. Kumu is making a holiday dinner for everyone at the decorated La Mariana. T.C. checks in to see how Rick is doing after Robbie's death. The handful of police remaining are overwhelmed on Christmas Eve. Magnum invites Lia to dine with him at La Mariana but she brushes him off. Honolulu P.D. is the victim of a ransomware attack seeking $5 million in bitcoin. Higgins attempts to use her backdoor into the HPD system. The gang gives Cade a truck as a Christmas gift and he acts strangely. The ransomware was uploaded from Lia's laptop. Lia has gone missing and ignores Magnum's call. Juliet tracks her to the home of Hawaii's biggest crime boss, Jonny Kim. Jonny is Lia's father. Lia thinks her half-brother Pin put the virus on her laptop after Jonny had fired him. Pin can't be found. Lia also tells Katsumoto about Jonny and Pin. The hacker now wants the ransom in cash, with the drop at a local mall. Barry helps Kumu with the meal. Magnum and Lia break into Pin's home. A fake IT tech, Lenny, has infiltrated HPD to abduct a witness, Mike Lazio. Pin is behind the abduction. Lia thinks of the Kim family cabin as a hiding place. Cade tells Rick that he's having trouble investing in such a large new family. Lia, Magnum, and Higgins go to the cabin. Magnum disguised as Santa provides a distraction for the other two, who take down Pin's thugs. Lia convinces Pin to surrender. Juliet suggests Thomas give Lia the benefit of the doubt. Kumu gives Barry a Playstation 5 console. Cade thanks his new family.