This Island Isn't Big Enough

When Rick's boat returns from a cruise deserted, Magnum searches for the answers to what has happened to his friend and the passengers on board, who are all presumed dead. His hunt is somewhat hampered by the separate investigation of a police detective who models himself on John Wayne, but as they both try to get to the bottom of the strange disappearance of the boat's passengers, they stumble upon a plot involving mobsters and two million dollars in counterfeit money.