Luther, and his secretary Blanche, come to Hawaii where Gillis is being given an award for his book.
- Tom Selleck as Thomas Sullivan Magnum IV
- John Hillerman as Jonathan Quayle Higgins III
- Roger E. Mosley as Theodore "T.C." Calvin
- Larry Manetti as Rick Wright
- Sheree North as Blanche Rafferty
- Geoffrey Lewis as Lloyd DeWitt
- Eugene Roche as Luther H. Gillis
- Jeff Harlan as Jack Gillis
- Kanani Choy as Big Sally
- Wallace W. Landford as Artie Keanu (credited as Wallace Landford)
- Jana Linden as Jo (credited as Jana Lindan)
- James C. Bertino as Scrungo (credited as Jim Bertino)
- Gabriel Aio as Little Tony
- James Carroll as Blackie
- Jake Hoopai as Guard
- A stock footage aerial shot of the St. Louis Gateway Arch is used for the opening scene.
- The Sony Walkman that Magnum uses while lounging in the hammock on the estate lawn appears to be the WM-10 model, the smallest cassettee-playing Walkman model.
- The wedding music at the end is "Clair de lune" by Claude Debussy.
- Higgins was in Albania (date unknown) where he was imprisoned in a zipper factory with Bertie Farnbush and his maiden sister, and used her hairpin to escape.
- Luther Gillis: Welcome to St. Louie. Maybe it ain't the best of towns, but it ain't the worst either. So what if the football team and the baseball team got to share the same nickname. Who cares, I call it home.
- Magnum: Higgins, I can explain.
- Higgins: I knew I could count on hearing that pathetic little phrase once again. It is as regular as the rising and setting of the...
- Luther Gillis: Computers are for sissies!
- Lloyd DeWitt: Oh, really. Well, let me tell you that computers and electronics are the wave of the future in this industry. Foot tails and stakeouts will become as obsolete as Panama hats and the ubiquitous informants out on the street. Be ready for the future, or you'll wind up in the past.
- Luther: Who said that?
- Lloyd DeWitt: I did. It's in my book, 'Private Investigative Techniques in the Computer Age: Software and You'. You can pick one up in the lobby for $7.95.
- Higgins: Please, Ms. Rafferty, I fail to see how some sordid detail from the past can have any relevance to our current plight.
- Blanche Rafferty: Hey, are you some kind of Duke or something, maybe a Count?
- Higgins: Ms. Rafferty, although the Higgins lineage is decidedly distinguished, it is not of the realm.
- Luther Gillis: I was beginning to get the feeling that I was stuck with the big guy for the duration. The only thing more depressing than that was this case, because we'd run out of leads. You try being a detective with no leads. It's like a tailor without a needle, or Godzilla without Tokyo, or... (Narration)
- Magnum: A bad guy without a motive. (Narration)
- Luther Gillis: Did you say something?
- Magnum: What?...Nope.
- Magnum: This was done by dot matrix.
- Luther Gillis: Who's dot matrix, and what's she got to do with this?
- Magnum: She's a computer, Luther!