Magnum and Higgins are each hired by a different spouse who are in the middle of a contentious divorce to dig up dirt on the other, and Thomas and Higgins soon find themselves competing over resources. Also, Rick and TC look into the death of an unidentified man and must share the news with his estranged daughter.

When a young man in need of immediate emergency surgery goes missing with a bullet lodged in his chest, Ethan asks Magnum and Higgins to find him before it’s too late. Also, TC talks to a military recruit who may be enlisting for the wrong reasons.

When Higgins is abducted, Magnum discovers its retaliation related to one of his first cases on the Island, and he, Rick and TC must break out an ex-client from prison in order to save her.

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.

As Magnum tries to keep his new relationship a secret and handles cases solo while Higgins is away, he is tasked with finding a single mom being hunted by two very dangerous gangs. Also, while Higgins is abroad with Ethan, a misstep forces her to assist an old employer, and Rick gets some bad, but also very, very good news.

A nun hires Magnum and Higgins to investigate a mysterious and large cash donation made to a parishioner undergoing medical treatment at the church. Also, Jin’s new dog walking business takes a dramatic turn, and Rick nervously prepares to reconnect with Suzy.

Higgins is in a complicated situation when 12-year-old Ella asks for help cracking a triple homicide that involves her mother. Also, Magnum bonds with Bob, a terminally ill veteran, while volunteering with the No Veteran Dies Alone Program and attempts to reunite him with his estranged family.

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.

Magnum and Higgins are sent on a deadly mission inside a high security correctional center when a ruthless criminal abducts Katsumoto and his ex-wife, Beth.

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 Rick make a shocking discovery in the Capt. Greene case. Higgins and TC head to Maui to help an eccentric billionaire find the owner of a pesky drone that has been harassing him. Shammy helps Kumu after an incident occurs at La Mariana.

An armed hit team lays siege to Robin's Nest. TC is badly injured while Rick fights for his life. Mid Season Finale

Magnum and Higgins try to help Zhao, a close friend of Kumu, recover her life savings that was all lost to a scammer. TC becomes increasingly frustrated at the lack of progress in his recovery and pushes everyone away.

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.

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 take a major step forward in their relationship. At the same time, the past comes back to haunt them when a previous suspect becomes their client. TC aims to scale up Island Hoppers. Rick gets a new business partner.