Heroin addict Daniel (Paolo Giusti) is knocked unconscious on a boat and winds up marooned on a tropical island inhabited by elderly escaped criminal Antonio (Arthur Kennedy) and his two grown up children, Haydee (Gemser) and Juan (Nicola Paguone). Daniel's presence on the island is naturally a concern for Antonio, who is still wanted by the law, but it also causes problems for Juan, who gets a little jealous when Haydee falls for the new arrival and no longer wants to play his special 'game' with him.
Emanuelle on Taboo Island is another random Gemser film that has since been retitled to cash in on the success in her Black Emanuelle series; but whilst it does admittedly offer Gemser fans plenty of opportunity to admire the dusky beauty in the buff, the movie itself is something of a bore, preferring to focus on the sensuality and romance of the situation rather than its more interesting and much sleazier themes (its main character's drug habit and the incestuous relationships between brother and sister, and father and daughter).
Towards the end things liven up a tad, with Antonio convincing Juan to try and kill Daniel so that they can get things back to how they were before he arrived on the island (you know—a spot of fishing, an afternoon nap, a bit of rogering a close blood relative): however, Daniel manages to talk sense into Juan, and so Antonio tries to finish the job himself. After a cliff-top tussle, the old man falls to his death.
The film closes with Daniel deciding to leave the island without Haydee, because he believes that, on the mainland, 'day by day, her smile will fade'. Instead she gets to stay with Juan, presumably to rekindle her incestuous affair and breed a small army of monstrously deformed children.
