When a married woman asks Magnum and Higgins to find her lover’s killer because she doesn’t want to expose the affair to the police, they find that the victim wasn’t who he claimed to be. Also, Rick visits Icepick, whose health has taken a turn for the worse.

When a Marine Corps vet’s SUV is stolen with her service dog inside, Magnum and Higgins must find the car, the dog and the car thief who they believe may be an escaped kidnapping victim. Also, when TC is sued by a disgruntled customer, he asks Rick and Jin to help prove that he’s being scammed.

When Rick is asked to assist with a federal investigation of his childhood friend Robbie, Magnum launches his own investigation to see what the Feds really have on him Also, Kumu goes undercover in a retirement community when Higgins is hired to investigate the disappearance of a resident’s life savings.

A Christmas Eve ransomware attack on the Honolulu Police Department forces Lia to reveal a family secret to Magnum and Katsumoto.

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.

Magnum and Rick race to find a missing witness who can exonerate an innocent man accused of murder. TC tries to repair his relationship with Mahina after being released from the VA.