Magnum and Higgins go to England to prepare Robin Masters' latest purchase, a castle, for a party. While there, Magnum looks up an old friend only to learn he is dead.
When he takes a job as a hotel detective, Magnum's attempts at catching a cat burglar preying upon guests are complicated by his relationship with a hooker who keeps getting him into trouble with both criminals and his boss.
Magnum goes home to Virginia to attend his grandfather's funeral. And when a family heirloom goes missing he accuses his step father of stealing it to save his business.
Robin Masters' publisher buries a chest containing $1 million on Oahu and a contest is held to find it. Magnum is tasked with protecting the woman who has the clues to the chest's whereabouts.
A woman who is writing a book about road signs hires Magnum because someone is following her and attempting to steal something but she does not know what it is.