Jason and Alexandra 'Alex', a close couple, loose their sail yacht in a storm and are grateful to get picked up by Captain Jim Bigelow's commercial carrier. Suspicous about the rough treatment and injections given by ship's doctor Gerbac which make the strong man faint, and realizing the ship is improbably empty and the radio not broke as the crew claims, Jason starts snooping around and finds human bodies on meat hooks, but even Alex thinks he's just hallucinating. Alas while sane Jason is restrained for his 'paranoia', the real madmen are the doc's genetic experiment outfit, who abuse their human captives as live incubators for a giant spider's eggs...