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.

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.

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.

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.