A woman from Bayonne, New Jersey hires Magnum for one day to find her fiancé.
Magnum is hired by Barbara Terranova, a financially broke woman who can only afford his services for one day, to find her missing fiancé Roger. But the case has several tangles in store when Magnum finds there are others searching for Roger too. Matters are complicated even further when T.C., desperate for some much-needed publicity for Island Hoppers, collars him into competing in the upcoming swim-run-bike Ironman triathlon. Fitness trainer Barbara trains him for the event in exchange for his extended help in locating her fiancé.
- 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
- Marcia Wallace as Barbara Terranova
- Curtis Credel as Agent Slim
- Jim Weston as Roger
- Louise Lewis as Wanda Barton (credited as Louise Fitch)
- Walt Davis as Chuck
- Darby Hinton as Buddy Moran
- Instantly recognizable actress Marcia Wallace is best known for her roles as receptionist Carol Kester on the 1970s sitcom The Bob Newhart Show and as the voice of Edna Krabappel on the animated series The Simpsons, for which she won an Emmy for Outstanding Voice-Over Performance in 1992.
- Magnum: Hawaii's like every sensual woman I've ever known. She can have raging, violent bursts of temper, followed by incredible calm, and peacefulness. Today was one of those days of true serenity, when even the great tourist wave seems to recede. (Narration)
- Magnum: I'm at ... Honolulu Lulu's pool hall.
- Higgins: (belly laugh) Honolulu Lulu's! I don't believe it. (laughs)
- Magnum: It's on the corner of Kahlua and Honaleki.
- Higgins: I'll send one of the gardeners over. Oh, and Magnum, don't forget to tell him what bus to take back. I wouldn't want him to make the wrong transfer, or whatever it is one does on a bus. (laughs)
- Higgins: You realize, of course, you have no chance of winning.
- (Magnum looks at the gun he's holding)