On the remote Petrie's Island off the east coast of
Ireland, farmer Ian Bellows goes missing and his wife contacts the local police.
Constable John Harris finds the farmer dead in a cave without a single bone in his body and fetches the island's physician, Dr Reginald Landers, who is unable to determine what happened. He journeys to the mainland to seek the help of a noted
London pathologist, Dr Brian Stanley. Stanley is unable even to hypothesize what could have happened, so both men seek out Dr David West, an expert on bones and bone diseases. Although Stanley and Landers interrupt West's quiet evening at home with jetsetter Toni Merrill, West is intrigued by the problem and agrees to accompany the two doctors back to Petrie's Island to examine the corpse. In order for them to reach the island quickly, Merrill offers the use of her father's private helicopter in exchange for the three men allowing her to come along on the adventure. Once back at Petrie's Island, Merrill's father's helicopter is forced to return to the mainland so he can use it, leaving the foursome stranded on Petrie. West and Stanley learn that a group of
oncology researchers led by Dr Lawrence Phillips have a secluded castle laboratory on the island. Paying a visit to Phillips' lab reveals that he and his colleagues are just as dead (and boneless) as Bellows. Reasoning that whatever it is must have begun in that lab, West, Stanley and Landers take Phillips' notes back to the inn where they are staying to study them. They learn that in his quest to cure cancer, Phillips may have accidentally created a new life form from the
silicon atom. Thinking the doctors are at the castle, Constable Harris bikes up there to tell them about the discovery of a dead, boneless horse, only to wander into the laboratory's "test animals" room and be killed by an offscreen tentacled creature, the result of Dr Phillips's experiments. The creatures, dubbed "silicates" by West and Stanley, kill their victims by injecting a bone-dissolving
enzyme into their bodies. The silicates prove difficult to kill, as Stanley, West and Merrill learn when Landers tries to kill one at the castle with an axe, but is himself killed. During this first encounter they learn that the silicates reproduce by dividing. Later discovering that they divide every few hours, the scientists calculate that the island will be totally infested in just a few days. After learning all they can from the late Dr Phillips's notes, West and Stanley recruit the islanders, led by Roger Campbell, to attack the silicates. Their initial attempts are unsuccessful. But when one is found dead, West and Stanley deduce the creatures can be destroyed using the rare
isotope Strontium-90. They obtain enough isotope to contaminate a herd of cattle and the silicates feed on these. At first, there seems to be no effect. Silicates break into the community hall and kill many islanders. West, Merrill, and some surviving residents barricade themselves in the clinic with Stanley until the Strontium 90 kills the silicates. The story ends with evacuation and medical teams inbound from the mainland, and West commenting on how fortunate they were that this outbreak was confined to an island. Had it happened on the mainland, he notes, they might never have stopped them in time. This sets up an epilogue and a visit to the satellite programme, in
Japan, where the technicians are duplicating Phillips' work with the inevitable result. A technician walks down a corridor, hears a strange noise and investigates before screaming. ==Cast==