Island of Terror

On Petrie's Island, farmer Ian Bellows disappears. The farmer's wife contacts local police. Constable John Harris finds the body in a cave, with all bones absent, an impossible condition that stuns the investigators. Dr Reginald Landers is summoned to help determine what happened.

Landers travels to the mainland to consult Dr Brian Stanley. Stanley is unable to determine the cause or provide a hypothesis. The two men decide to bring in Dr David West, an expert on bones and bone diseases.

Stanley and Landers interrupt West's quiet evening at home, where jetsetter Toni Merrill is present. West agrees to accompany them to Petrie's Island to investigate the mysterious corpse. The prospect of a difficult case finally motivates him to join.

Merrill offers use of her father's private helicopter to reach the island more quickly. The three men accompany her aboard, turning the journey into a four-man expedition. They set off to Petrie's Island with grand hopes of answers.

Upon arrival, Merrill's father takes the helicopter back to the mainland; the four scientists are stranded on Petrie's Island. They realize they must proceed by ground and rely on local contacts. The island’s isolation tightens the clock on the mystery.

West and Stanley learn there is a secluded castle laboratory on the island run by Dr Lawrence Phillips. A visit to the lab reveals that Phillips and his colleagues are dead, boneless, suspiciously missing bones.

They examine Phillips' notes and uncover his risky attempt to cure cancer by creating a new lifeform from silicon. The findings explain the horrific victims but raise more questions about the nature of the threat. The scientists realize the danger extends beyond isolated experimentation.

Constable Harris bikes to the castle to warn the scientists, only to stumble into the lab’s 'test animals' room and be killed by an offscreen tentacled creature. The creature seems to be a product of Phillips's experiments. The incident confirms the danger is real and immediate.

The creatures are dubbed 'silicates' and kill by injecting a bone-dissolving enzyme. West and Stanley learn that the silicates reproduce by dividing, a process that could infest the island within days if unchecked.

The group attempts to kill silicates with bullets, petrol bombs, and dynamite; nothing harms the creatures. The islanders face mounting danger as the infestation spreads. The heroes realize more drastic measures are required.

A dead silicate is found to have ingested Strontium-90 from Phillips' irradiated lab, revealing a vulnerability. West and Stanley decide to contaminate remaining silicates with isotope to halt the infection. Their plan requires obtaining Strontium-90 from the castle.

West and Stanley obtain enough Strontium-90 to contaminate a herd of cattle, at the cost of Stanley's left hand when grabbed by a silicate. The cattle become a weapon against the silicates as they ingest the isotope.

The silicates feed on the contaminated cattle and attack the community hall; West, Merrill, and surviving locals barricade themselves in the clinic with Stanley. In a climactic effort, the silicates are repelled and all die in the hall.

Medical teams begin evacuation from Petrie's Island as the threat ends. West notes the outbreak's containment on an island prevented a broader catastrophe. The epilogue follows a Japanese satellite program duplicating Phillips' work, ending with a technician hearing a strange noise and screaming.