A Christmas Eve ransomware attack on the Honolulu Police Department forces Lia to reveal a family secret to Magnum and Katsumoto.

Magnum and Higgins weigh the risks of pursuing a relationship. Rick juggles being a new father and running La Mariana. Katsumoto tries to figure out his next move.

Magnum and Higgins’ new clients hire them to find their missing brother last seen on the island, leading to Higgins being shot and TC abducted when a secret case of revenge is revealed during the investigation. Also, Higgins (and Magnum!) are surprised when her surgeon asks her out.

While Magnum and Higgins reunite and work the case of a construction worker’s tragic death, TC and Shammy get skyjacked by a pair of drug runners posing as tourists.

Magnum, Higgins and Rick go undercover at a ritzy country club when a young caddie is fired after being accused of stealing a member’s golf clubs. Also, Jin’s niece, unaware of her uncle’s shady past, asks him to speak at her school.

Higgins’ therapist hires her to look into why one of her teenage patients died of suicide.

When Magnum and Higgins are hired by an anxious groom to look into his bride-to-be on the eve of their wedding, what they think is a simple case of cold feet turns into a web of lies and a life-or-death situation for Higgins. Also, TC makes a touching decision on how to help Cade.

A journalist hires Magnum to track down his anonymous source after they mysteriously go dark, and Higgins receives a new assignment from MI-6. Also, Rick’s old friend comes to the island, but TC is suspicious of his motives.

When Rick is asked to assist with a federal investigation of his childhood friend Robbie, Magnum launches his own investigation to see what the Feds really have on him Also, Kumu goes undercover in a retirement community when Higgins is hired to investigate the disappearance of a resident’s life savings.

Magnum starts following Higgins to discover what she’s been hiding, as she’s secretly assigned to infiltrate a group threatening to take down MI-6. Rick struggles after an explosion takes the life of someone important to him.

When Hawaii Supreme Court nominee Judge Rachel Park is being blackmailed, she hires Magnum and Higgins who go to extraordinary lengths to help her out. Also, with the pressure of fatherhood looming, Rick suggests changes to make La Mariana more profitable, but TC and Kumo aren’t swayed.

A bail bondsman hires Magnum and Higgins to track down a woman who skipped out on her $250,000 bond. When they locate the body of another P.I. who was previously searching for her, they partner with Det. Lia Kaleo on the case. Also, T.C. and Katsumoto team up on an emotional search for Cade’s mother.

When Magnum balks at notorious crime boss Osi Shima’s (Eijiro Ozaki) request to find his missing son, Magnum learns he’s been poisoned and has only eight hours to locate Shima’s son to earn the antidote, or else he dies.

The mother of a suspected bomber hires Magnum and Higgins to locate her teen son and turn him in to the authorities. Also, Kumu and Rick help T.C. navigate his guilty conscience when he runs into a past flame.

As Magnum tries to keep his new relationship a secret and handles cases solo while Higgins is away, he is tasked with finding a single mom being hunted by two very dangerous gangs. Also, while Higgins is abroad with Ethan, a misstep forces her to assist an old employer, and Rick gets some bad, but also very, very good news.

A nun hires Magnum and Higgins to investigate a mysterious and large cash donation made to a parishioner undergoing medical treatment at the church. Also, Jin’s new dog walking business takes a dramatic turn, and Rick nervously prepares to reconnect with Suzy.

Shammy asks Magnum and Higgins to locate his missing friend, a homeless veteran. Also, T.C. tries to get Cade to return to school, but quickly learns it’s not that simple.

Magnum goes to extreme lengths to uncover the truth about a crime that may have involved his dear deceased friend, Nuzo.

Magnum and Higgins are sent on a deadly mission inside a high security correctional center when a ruthless criminal abducts Katsumoto and his ex-wife, Beth.

Magnum and Higgins go undercover as lifeguards in order to solve a murder. Jin Jeong wins a storage unit auction and enlists the help of Rick and TC upon finding a stolen military medal.

Katsumoto takes a job providing security for a chart-topping K-pop star. Higgins and Rick find themselves in peril while trying to help Rick's friend. Magnum harbors suspicions about Capt. Greene's death.

Katsumoto's hearing date has arrived and he will learn if his career in law enforcement is over for good or not. Magnum and Higgins are hired to investigate a man their client believes committed murder. Rick's suspicions grow on their relationship.

Magnum and Higgins investigate the robbery of an elderly man suffering from Alzheimer’s. The ohana tries to help TC overcome a past trauma.

Magnum and Rick make a shocking discovery in the Capt. Greene case. Higgins and TC head to Maui to help an eccentric billionaire find the owner of a pesky drone that has been harassing him. Shammy helps Kumu after an incident occurs at La Mariana.

Magnum and Higgins take on a case that sends Higgins inside a psychiatric hospital. Katsumoto and his son, Dennis, head to the mainland to look at colleges, but their trip takes a harrowing turn when a run-in with a local turns ugly.