Some peculiar goings on going on on this island! On the remote Petrie’s Island off the east Irish coast a farmer goes missing and his wife contacts the police. Constable John Harris (Sam Kydd) goes looking for him and finds him dead in a cave without a single bone in his body. Horrified, Harris swiftly fetches the town physician Dr. Reginald Landers (Eddie Byrne) but Dr. Landers is unable to determine what happened to the dead man’s skeleton. Landers journeys to the mainland to seek the help of noted London pathologist Dr. Brian Stanley (Peter Cushing). Like Landers, Stanley is unable to even hypothesize what could have happened to Ian Bellows, so both men seek out Dr. David West (Edward Judd) an expert on bones and bone diseases. Although Stanley and Landers interrupt West’s dinner date with the wealthy jetsetter Toni Merrill, West is intrigued by the problem and so agrees to accompany the two doctors back to Petrie’s Island to examine the corpse. In order for them to reach the island that much faster, 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 effectively stranded on Petrie until the helicopter can return. West and Stanley learn that a group of cancer researchers led by Dr. Lawrence Phillips (Peter Forbes-Robertson( seeking a cure for cancer, 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 Ian Bellows. Reasoning that whatever it is must have begun in that lab, West, Stanley and Landers gather up Phillips’ notes and take them to study them. From them they learn that in his quest to cure cancer, Phillips may have accidentally created a new lifeform from the siliconatom. Thinking the doctors are at the castle, Constable Harris bikes up there looking for them to tell them about the discovery of a dead, boneless horse, only to wander into the laboratory’s “test animals” room and be attacked and killed by an offscreen tentacled creature, the result of Dr. Phillips’ experiments. The creatures are eventually dubbed “silicates” by West and Stanley, and kill their victims by injecting a bone-dissolving enzyme into their bodies. The silicates are also incredibly difficult to kill, as Landers learns when he tries and fails to kill one at the castle with an axe when they first encounter them. After learning all they can from the late Dr. Phillips’ notes, West and Stanley recruit the islanders, led by “boss” Roger Campbell (Niall McGinnis) and store owner Peter Argyle (James Caffrey, who seems to serve as Campbell’s second-in-command in an unofficial capacity), to attack the silicates with anything they’ve got. Bullets, petrol bombs, and dynamite all fail to even harm the silicates. But when one is found dead, apparently having ingested a rare isotope called Strontium-90 from Phillips’ lab (via Phillips’ accidentally irradiated Great Dane), West and Stanley realise they must find more of the isotope at the castle and figure out how to contaminate the remaining silicates with it before it is too late. They obtain enough isotope to contaminate a herd of cattle – at the cost of Stanley’s left hand, when he’s grabbed by a silicate – and the silicates feed on these and begin to die. The story ends with evacuation and … a twist. Rather unsatisfying outing from Hammer, despite the icky slimy tentacled monster and the expansive cast which also includes several Irish actors – making up for the lack of a location shoot (it was made at Pinewood). The most interesting part of this action-adventure-disaster is the electronic soundtrack by Malcolm Lockyer and the cool helicopters which photograph rather marvellously.