Luther Gillis is a private investigator from St. Louis who was hired by the father of a 16-year-old runaway girl to find her. At the same time, Magnum was hired by the girl's mother to find her. Can they work together?
Rick's old friend Waldo Norris is caught trying to break into a guarded building. Waldo claims he is working for an insurance company and is investigating the loss of a valuable figurine.
Rick's 22-year-old sister Wendy arrives in Hawaii. Rick still believes that she is a young, innocent girl and asks Magnum to entertain her while Rick works at the club.
Investigating a series of convenience store robberies, Magnum also comes across a couple of elderly ladies, who live in a broken-down house with other elderly people who are being harassed by a no-good slum lord.
Magnum is in Detroit and TC is using the Ferrari. While driving the car, TC has an accident and injures a bare knuckles fighter and he has to take his place in the ring.
Holly Fox was a DJ in Vietnam admired by all the servicemen including Magnum, TC and Rick. While listening to the radio one day, Magnum hears a voice that he believes is Holly Fox.
It's Christmas time and TC is flying Magnum (dressed as Santa Claus), Rick and Higgins to three different islands. En route, TC is forced to make an emergency landing on an island that the Navy uses for gunnery practice.
The Jororo Islands youth baseball team is in Hawaii to play TC'S All-Stars. The Jororo center fielder is 12-year-old Prince Danny who is a target of Jororian dissidents.
Assistant District Attorney Carol Baldwin was removed as prosecutor of a major criminal case and then fired. She enlists Magnum's help in finding evidence against the man she was prosecuting.
A woman whose father was just released from prison approaches Magnum asking him to follow her father to ensure he does not commit a crime. Thomas ends up trapped in a bank vault with the woman.
While getting mixed up in a car chase with a couple of fencing suspects, Magnum is responsible for injuring an innocent bystander and brings her from the hospital to Robin's Nest.