Fact1: UN troubleshooter Alan Brooks in same train compartment as goes to Trollenberg 's observatory sisters, Fact2: always-stationary radioactive cloud is observed on mountain 's south face, Fact3: similar incidents took place in Andes, Fact4: hut being locked from inside, Fact5: first rescuer there finds rucksack with severed head inside
Output: On the Swiss mountain Trollenberg, one of three student climbers is suddenly killed, his head ripped from his body. Two sisters, Anne Munro and Sarah Pilgrim Jayne, a London mindreading act, are travelling by train to Geneva when Anne faints as the train passes the mountain. Upon waking, Anne insists that they must get off at the next stop. UN troubleshooter Alan Brooks Tucker, in the same train compartment as the sisters, goes to Trollenbergs observatory, where Professor Crevett Warren Mitchell explains that, despite many climbing accidents, no bodies are ever found; an alwaysstationary radioactive cloud is regularly observed on the mountains south face. Brooks learns that similar incidents took place in the Andes three years earlier, before a similar radioactive cloud vanished without a trace. Local rumours circulated that something was living in the mist. Anne is giving a mindreading demonstration at the hotel when she sees two men in a base camp hut on the mountain: Dewhurst Stuart Saunders is asleep when the other man, Brett Andrew Faulds, under some kind of mental compulsion, walks outside. Meanwhile, the cloud has enveloped the hut. Anne suddenly faints again, and Brooks phones the hut but no one answers. A rescue party ventures to the hut looking for both men. Anne, in a trancelike state, urges the rescuers to stay away. Inside the hut, the group discover that everything is frozen solid, despite the hut being locked from the inside. Dewhursts body is found under the bed, its head missing. A spotter plane arrives and circles overhead, and a man is seen off in the distance. At his location, the first rescuer there finds a rucksack with a severed head inside. He is quickly set upon and killed by Brett, who later attacks and kills a second rescuer. Now at the hotel, Brett storms in and launches an attack on Anne. The men manage to subdue him, and during the struggle Brett sustains a severe head gash, but no blood flows from the wound. Brett is heavily sedated and locked away. Brooks recalls a similar incident in the Andes that followed a similar pattern: a man murdered an elderly woman who allegedly possessed psychic abilities just like those displayed by Anne. The killers body was discovered to have been deceased for at least 24 hours prior to his murder of the old women. Brett escapes his improvised cell and resumes his hunt for Anne, this time armed with a small hand axe. Before he can reach Anne, he is quickly shot and killed by Brooks. The cloud has begun to move down the mountainside towards the hotel, so the group retreats to the heavily fortified observatory. As they enter the cable car, a mother realises that her young daughter is missing. In a thickening mist a giant, multitentacled creature with a single huge eye appears at the hotel, smashing down the front door. Brooks manages to rescue the child from the lobby, both of them narrowly escaping its grasp. They return to the cable car, but the delay has given the thickening mist a chance to reach the car platform. The transport motor begins to freeze, starting and stopping, the cable slipping, but the cable car arrives safely. The single cloud has now split and become four while converging on the observatory. Hans Colin Douglas, who left the hotel, suddenly turns up at the observatory. Once inside, he begins exhibiting the same obsession with Anne. Hans tries to strangle her, but the group can only stop him by killing him. As the tentacled monsters near the observatory, everyone makes Molotov cocktails to combat them. By radio, Alan orders an aerial firebombing raid against the observatory, which has a reinforced concrete roof and walls that can withstand the assault. Journalist Philip Truscott Payne strikes one of the creatures with a Molotov cocktail, setting it ablaze. He is caught from above by one of the tentacled monsters on the observatorys roof. With another Molotov cocktail, Brooks sets that one ablaze, forcing the burning creature to release Truscott. Later, Truscott does the same as another oneeyed monster manages to breach a thick wall, trying to get at Anne. The aerial firebombing assault begins and is successful at torching the remaining creatures.