Magnum and Higgins take a major step forward in their relationship. And the past comes back to haunt them when a previous suspect becomes their client. TC aims to scale up Island Hoppers.

Magnum and Higgins reexamine 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.

Magnum and Higgins are hired by a University of Oahu dean to quietly investigate a professor who has been accused of having an inappropriate relationship with a female grad student.

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.

Magnum and Higgins agree to help a teenage Amish boy who has traveled to Hawaii in search of his runaway sister. Rick sets out to find TC a date to the Marine Corps Ball.

Magnum and Higgins are hired to find a missing gamer whose online friends believe he might be in trouble. Jin Jeong enlists the help of TC in a treasure hunt after his ex-partner leaves prison.