On the remote Petrie's Island off the east coast of Ireland, Ian Bellows, Liam Gaffney, vanishes and his worried wife contacts the local police. Constable John Harris, Sam Kydd, is the first to uncover a chilling scene: the farmer’s body lies in a cave, nearly bone-dissolved and devoid of structure, leaving him with more questions than answers. The island’s physician, Eddie Byrne as Dr. Reginald Landers, is unable to make sense of the bizarre transformation, and together they decide to seek help from the mainland. They turn to a renowned London pathologist, Dr. Brian Stanley, Peter Cushing, who arrives with a calm, methodical curiosity but finds the mystery just as baffling as the locals.
Seeking broader expertise, the team enlists Dr. David West, Edward Judd, an expert on bones and bone diseases. West, Stanley, and Landers are interrupted at a quiet home by jetsetter Toni Merrill, Carole Gray, who is intrigued by the case and proposes she accompany the three scientists back to Petrie’s Island. Merrill’s offer includes the use of her father’s private helicopter, a high-speed shortcut that could accelerate their investigation. Reluctant but hopeful, the men accept the help and set off to uncover the truth.
Back on the island, Merrill’s father’s helicopter is recalled to the mainland to free the craft for essential use, leaving the group stranded. As they dig deeper, they discover a secluded castle laboratory run by oncology researchers led by Dr. Lawrence Phillips, Peter Forbes-Robertson. The researchers’ work appears connected to cancer treatment, but there is a disturbing undercurrent that hints at dangerous experiments. A visit to Phillips’ lab reveals that he and his colleagues are dead—bone structure and all—yet the investigators soon realize the same fate has befallen others on the island. The bones tell a story that something new and terrifying has been created.
Back at the inn, West and Stanley pore over Phillips’ notes and realize that the quest to cure cancer may have produced a wholly new lifeform. They suspect that the experiments yielded a silicon-based organism, capable of reproduction and rapid spread. In a chilling turn, Constable Harris bikes up to the castle to warn them, only to enter the laboratory’s test-animals room and be killed by an offscreen, tentacled predator born from Phillips’s experiments. The creatures are soon named “silicates,” and they attack with a chilling efficiency, injecting a bone-dissolving enzyme into their victims.
The threat proves stubborn and relentless. The silicates reproduce by division, doubling their numbers every few hours, and the scientists quickly calculate that an island-wide outbreak could happen within days. West, Stanley, and Merrill press on, hoping to find a weakness. They learn that a crucial isotope, Strontium-90, appears key to ending the threat, and they race to contaminate the silicates with the isotope to halt the spread. Their pursuit takes a heavy toll: in a pivotal moment, Stanley loses his left hand when seized by a silicate, and Landers is killed while attempting to strike at the creature.
With time running out, West and Stanley rally the islanders, led by Niall MacGinnis as Roger Campbell, to mount a desperate defense using every available resource—bullets, petrol bombs, and dynamite—against the seemingly invincible invaders. The plan hinges on distributing enough Strontium-90 to disable the remaining silicates, and they manage to contaminate a herd of cattle to deliver the isotope to the creatures. The strategy tests everyone’s resolve as the community hall fills with silicates that overwhelm the makeshift defenses, killing a number of islanders.
In a tense standoff, West, Merrill, and a dwindling group of survivors barricade themselves in the clinic while the silicates close in. The battle reaches a critical moment as the surviving silicates succumb to the isotope, and the remaining threat collapses. The islanders begin to evacuate as medical teams from the mainland arrive, and West reflects on the narrow escape: had this outbreak occurred on the mainland, stopping it might have been a far more daunting task.
The story closes with a stark epilogue hinting at a broader scope. A satellite program in Japan is shown attempting to replicate Phillips’ work, suggesting that the dangerous potential lives on beyond Petrie’s Island. A technician walks down a corridor, hears an eerie noise, and screams, leaving an uneasy sense that the nightmare could recur elsewhere.
- The isolated setting, combined with a race against time and an eerie new lifeform, fuels a brisk, methodical thriller that blends scientific inquiry with survival drama.
- The characters’ collaboration—Dr. West, Dr. Stanley, Dr. Landers, and the island community led by Roger Campbell—forms the emotional core, while the danger posed by the silicates drives the escalating tension.
- The film fuses procedural investigation with visceral horror, inviting viewers to contemplate the consequences of unchecked experimentation and the fragility of a seemingly quiet island under siege.
