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.
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.
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.
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.
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.
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 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.
