Das schöne Inselmädchen Alealea und Magnum sind die einzigen Augenzeugen eines Mordes. Vogel, der skrupellose Killer, schießt deshalb auf die beiden. Die versuchen, sich durch einen Sprung ins Wasser zu retten, aber Thomas wird durch eine Kugel schwer verletzt. Als er wieder zu sich kommt, befindet er sich in Alealeas Begleitung auf der verbotenen Insel. Noch delirierend warnt Magnum den Stammesältesten vor dem Killer, der nicht zögern wird, in das letzte Refugium der hawaiianischen Urbevölkerung einzudringen.
Magnum is working on a case before a date with Rick's visiting cousin, when he sees a young native Hawaiian girl become an accidental witness to a murder. With the gun-man after her, Magnum saves the young woman as they escape by diving into the sea, and is injured with a gun-shot wound in the process. He regains consciousness several days later on the remote, secluded island of Kapu, after being rescued by a native fisherman from the island, and suffering from a hazy memory of the incident. There is no sign of the girl, and the island natives insist that he was the only one found. Thomas tries to remember the events that lead to him being on the island, and what has happened to the girl, but as he tries to uncover the secrets of the island and its people, it begins to seem more and more as if they don't want him to find any answers or to leave... Meanwhile, the killer is still looking for the girl, to eliminate her as the only witness to the killing...
Une jeune Hawaïenne, Alealea, est témoin du meurtre de Nick Sutherland. Le meurtrier veut désormais se débarrasser d'Alealea mais Magnum intervient...
Magnum sta lavorando a un caso e si prepara per un appuntamento con la cugina di Rick che si trova in visita alle Hawai, tuttavia assiste una giovane del posto in difficoltà quando la ragazza si trova coinvolta in un omicidio. Inseguiti da uomini armati, scappano via mare, ma Thomas viene ferito da un colpo di pistola. Riprende conoscenza dopo alcuni giorni e si ritrova sulla remota isola di Kapu, ma della ragazza non c'è traccia. Magnum ha dei ricordi confusi circa l'accaduto ma le sue domande non trovano risposta e sembra anzi che gli abitanti dell'isola stiano nascondendo qualcosa.
