After her archaeologist father's boat is found deserted at sea in the Nihoa Channel, a marine biology student hires Magnum to find out what happened to him. The local natives warn Magnum to stay away from the "cursed" channel, but he's determined to find out what happened to the missing man.
Magnum dons his sailor's cap when a young marine biologist hires him to take on supposedly cursed waters and find out what happened to her missing archaeologist father.
- 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
- Jeff MacKay as Lieutenant McReynolds
- Wendy Girard as Marion Hammond
- Ina Balin as Professor Martinez
- Mamaluna as Tehani
- Curtis Malia as Keone
- Roger E. Mosley is credited, but do not appear.