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?
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.
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.