Magnum and Higgins search for a CEO who has mysteriously vanished. Rick braces for a visit from his wild-child little sister, Ruthie.

When a woman hires Magnum and Higgins to locate a man she met briefly at a coffee shop and felt a spark with, they learn that he is hiding a big secret. Also, Higgins keeps a secret of her own after she has a romantic dream about Magnum.

Magnum and Higgins are shocked when one of her former MI6 teammates shows up with a fresh gunshot wound and news that "the Viper," the assassin who killed Higgins' true love, has surfaced on Oahu. Also, while Magnum's busy helping Higgins track down the Viper, he asks Rick to take over a case, a task that Rick relishes until it goes sideways.

Magnum recruits Katsumoto to help find a missing tourist. Higgins and Kumu attempt to solve the murder of a beloved dog. Rick enlists the aid of TC after he accidentally loses Magnum's pet mouse, Roberto II.

Magnum takes a case from fellow private investigator Luther Gillis to find the true identity of a man’s comatose fiancée when he learns that she’s had extensive facial surgery.

A close friend of Higgins, an art connoisseur who recently hired Magnum to test his security, is murdered, and Thomas is arrested as the main suspect.

Magnum takes the case of a little girl’s missing cat and, in the process, stumbles upon another cat’s murdered owner who happens to be an FBI agent.

Magnum, flooded with memories of his tour in Afghanistan, helps his fallen friend’s brother search for a now-grown Afghan boy who may have been a victim of trafficking.

A decorated former Navy SEAL who, upon returning home from Afghanistan, repurposes his military skills to become a private investigator in Hawaii.

Magnum helps Dan, a struggling fisherman and fellow veteran, when his 300-pound tuna worth $350,000 is stolen, and he discovers that the thief needs Magnum's help as well.

TC asks Magnum to take on a case to help acquit the father of one of his young football players, who is accused of murder.

An aging tycoon asks Magnum to find his lost love who he says just recently contacted him; the only problem is she died 30 years ago. Also, Rick and TC meet a fellow vet who is having a hard time adjusting to civilian life.

A man dying of lymphoma hires Magnum to find his estranged, bone-marrow-compatible brother who turns out to need Magnum’s help as well. Also, Magnum’s case brings back haunted memories for the guys of a past SEAL team mission that went sideways.

Magnum must help Rick’s crush, Toni, after her illegal poker game, organized to pay back a mob debt, is robbed by masked gunmen.

As Magnum helps a woman find her missing cousin, Sergei, a Russian fugitive, Higgins' and Kumu's lives are put in danger when they get too close to the case.

Magnum has an emotional connection to a case when he and every other private investigator and bounty hunter on Oahu are tasked to track down a man accused of murder.

A man hires Magnum to investigate his own murder before he is killed. Kumu reconnects with an old friend.

Magnum discovers that his ex, who landed him and his friends in a POW camp, is on the island and planing to steal a fortune in gold.

Magnum is hired by a woman to prove that her son didn't kill his girlfriend and has only 24 hours to do so before the accused accepts a plea deal. Also, Rick and TC try to recover stolen appliances that were donated to a wounded veteran.

After a man is murdered, Magnum poses as a doctor on the same dating app the victim was using in order to find the killer who may be praying on wealthy men.

When the Dobermans dig up what appears to be a human bone, Magnum and Higgins help Katsumoto investigate the murder of his former mentor.

As their wedding day approaches, Magnum and Higgins help a modern-day Robin Hood who, thinking she was helping a school obtain needed supplies, unknowingly stole illicit drugs. Also, Rick helps a retired soldier with the difficult task of re-entering the work force as a civilian.

After a 16-year-old kidnap victim, Amanda, escapes her captors, her parents hire Magnum, who experienced similar trauma as a POW, to find who took her.

When Magnum and Higgins get “yacht-jacked,” Higgins is shot and she and Magnum are stranded at sea, struggling to reach land before she bleeds out and the culprits return to finish them off.

Hannah, Magnum's ex and the fugitive responsible for him and his SEAL team brothers being POWs for years, shows up at his home with a gunshot wound, and wanting his help to find her missing CIA father whose life is in danger. Also, Magnum makes an earnest proposition to Higgins for her to become his private investigations partner.