Several people disappear from and at the sea. Their bodies are found gnawed to the skeleton, even the marrow is missing. The scientists have no idea which animal could do such things. Dr. Turner begins to suspect that the company which builds a tunnel beneath the bay might have poisoned the environment and caused an octopus to mutate to giant dimensions. Just at the same time a great sailing regatta with many children is started - among them Turner's nephew Tommy.
John Huston, Shelley Winters, Bo Hopkins, Henry Fonda, Delia Boccardo, Cesare Danova, Alan Boyd, Sherry Buchanan, Franco Diogene, Marc Fiorini, Helena Mäkelä, Claude Akins, Alessandro Poggi, Roberto Poggi, Giancarlo Nacinelli