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.

Kumu and Higgins are in danger when Robin's Nest is under siege by mercenaries storming the estate in order to find out the true identity of the White Knight, Robin's muse and literary hero. Also, Rick and T.C. helps one of Rick's employees when his car is stolen, and Higgins finally gives Magnum an answer about if she'll become his partner.

As Magnum, Higgins and TC try to pull one over on a customs agent to get Higgins a green card, armed gunmen suddenly storm the federal building and start taking hostages.

Magnum and Higgins help an up-and-coming mixed martial arts fighter who is being pressured by a gang to throw an illegal fight. Also, Kumu is arrested for stealing an artifact from a collector that should be returned to its original resting place.

When a wealthy man hires Magnum and Higgins to find his missing wife, they are stunned when a tragedy occurs as a result of their investigation. Also, Kumu's suspicion of her step-daughter's boyfriend creates a divide with her and Kumu's new relationship.

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 disoriented man hires Magnum and Higgins to investigate a crime he doesn’t remember after he woke up on the beach covered in blood. Also, T.C. is taken aback when Cade’s biological grandmother makes a surprise visit, and Rick’s feelings for Suzy grow stronger as they prepare for the birth of their first child.

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.

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

Magnum and Higgins re-examine a fatal arson investigation at the request of TC and Mahina, leading to a sinister discovery. Kumu volunteers with Rick at a veterans’ crisis call center.