Magnum is preparing for this year's big surf-ski race, while in a chance meeting, Higgins meets Lady Wilkerson, an English Duchess whom he has been smitten with after two brief encounters years before (which she does not identify him from). She is in the islands incognito, and must sell some valuable family jewels after being strapped financially, but Higgins ends up saving her from two men who accost her in an alleyway. As smitten with the woman as ever, Higgins offers her a job on the Estate, and plans to reveal his feelings towards her via a letter, but due to a mix-up and misunderstanding, she assumes the letter to be from Thomas instead, whom it becomes apparent she has eyes for, blind to Higgins' desires. But these confused matters of the heart seem trivial when the Duchess is kidnapped by the two men who had made a grab for her previously...

T.C. drags a reluctant Magnum along to the newly-opened club of an old flame – a beautiful jazz singer who he fell in love with in Vietnam – who has just moved to the islands. Thomas doesn't dislike the woman, but insists to T.C. that trouble always follows her wherever she goes – but T.C., still infatuated with the girl, refuses to listen. But sure enough, the woman is in trouble, searching for a man who owes her $18,000 and mixed up with Detroit drug dealers that are out to kill her...

While Higgins is preparing to direct a selection of pieces from Gilbert and Sullivan's 'The Mikado' to be staged at the Estate, Thomas is hired by an attractive young woman to find her missing brother, who she claims has disappeared after joining a religious cult. The girl has musical experience and agrees to help out with rehearsals of Higgins' production while Thomas seeks out her missing brother, but Thomas uncovers more than he expects and finds himself dealing with a radical political group and an assassination attempt revolving around a visiting cast member of Higgins' production...

Thomas is hired by Jack Damon, Carol's Uncle, to find his seventeen-year-old daughter Becky, who has been missing for two months, after leaving home against his wishes to pursue a career as a dancer. After a little investigating, Thomas finds that the last person known to have seen the girl was her former boyfriend Darryl Jacobs – who is now behind bars after being involved in a stolen guns deal that went bad. Magnum decides the only way to find out from Jacobs what happened to Becky is to go undercover as a convict at the prison farm where Jacobs is being detained...

T.C. is giving Thomas helicopter flying lessons when he is shot. With T.C. hospitalised, Mac appears on the scene, ""volunteering"" his services to stand in running Island Hoppers. But it seems that the assailants were actually gunning for Magnum, after a week previously, somebody impersonated him when trying to blackmail a Mexican Mafia King. With Magnum marked as a dead man as a result of the mistaken identity, confusion and chaos reigns, and as per usual, Mac 'just happens' to be in the middle of it all...