Magnum sees a native Hawaiian girl witness a murder. When the gunman goes after her, Magnum intervenes and both escape into the sea. The gunman shoots Magnum, who loses consciousness. When he awakens a few days later on the secluded island of Kapu, he remembers little about the incident - and it seems the island's residents don't want to help him learn any more. But the gunman and the girl are still out there somewhere...