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.

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

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 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.

Magnum and Higgins enlist Katsumoto to go undercover when a chef at a high-end restaurant goes missing. Kumu works with Cade at the Cultural Center, confronting one of America's darker chapters - the internment of Japanese Americans in the wake of Pearl Harbor.

After a high-stakes homicide case falls apart at trial, Katsumoto asks Magnum to help him stop a killer from walking free. Higgins helps Jin Jeong with a mystery of his own.