When Higgins asks his help in finding Robin's latest manuscript after it is stolen, Magnum gets some unexpected help in the case when St. Louis gumshoe Luther H. Gillis (Eugene Roche) arrives unannounced on vacation. They set about trying to work out who is so desperate to get hold of the manuscript that they are willing to resort to attempting to kill Higgins and drugging Zeus and Apollo to get it, in scenes reminiscent of those portrayed in the stolen 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