“His head – it was torn orf!”

On a mountainside, Johnny leaves his two climbing mates and climbs on alone. He shouts down that there’s someone coming, screams, and his body plummets past his puzzled friends, still attached to them by a rope. They pull him back up, but as the body comes back into view his friend cuts it loose. “Didn’t you see?” he explains to his mate. “His head – it was torn orf!”

No respectful laying to rest for partial corpses in 1958 then, clearly.

Meanwhile, Sarah and Anne Pilgrim (Jennifer Jayne and Janet Munro) are making their way through Switzerland on the train. They are The Pilgrim Sisters, a mind reading act on their way to Geneva. As Anne spots the Trollenberg mountain through the train window, she faints into the lap of a handy square-jawed American, wakes up and tells Sarah they’re getting off at the next stop. This also happens to be the stop for their new American friend, Alan (Forrest Tucker, again), who is there to visit his friends at a nearby observatory.

As the girls make themselves comfortable at the village’s only hotel, Alan goes up to the observatory (or more specifically, a big empty room with a couple of small telescopes set up by the window) which is being run by friendly Professor Crevett (Warren Mitchell, doing his best “Einstein” impression). Alan is told that for the past few months, people have been disappearing into a radioactive cloud which sits stationary on the side of the mountain, never to return. The observatory, which also happens to be avalanche-proof (hmm, sounds like it might come in handy later on) has been keeping an eye on the cloud. And of course, that’s quite enough worrying about that. Because if we know nothing else from this seemingly never-ending parade of black and white British sci-fi/horror hybrids, radioactivity is absolutely nothing to worry about, chum. Until it is.

Back at the hotel, Anne has been showing a remarkable psychic ability for one half of a vaudeville mind reading act. As the cloud begins to move up and down the side of the mountain, picking off yet more mountaineers, she seems to have developed a kind of psychic link with it. As the deaths continue, it becomes apparent that not everyone is being killed outright – a hotel guest called Brett (Andrew Faulds) appears to have been taken over by SOMETHING and bludgeons his supposed rescuers to death with a pickaxe (in an astonishingly brutal scene). He arrives back at the hotel, looking dishevelled and sweaty, and goes on to prove his newfound inhumanity by being unable to light a cigarette. He attacks Anne and is punched out by Alan, falling back and cracking his head on a nearby statuette with enough force to kill him. But when Alan checks out the body, there’s no blood.  Alan surmises that this can only mean one thing. “Are you trying to tell me that… we’ve just been fighting a… dead man?” stammers another hotel guest.

In order to progress the plot a bit (in the way these sub-90 minute features were wont to do), the Professor has already jumped to the remarkable conclusion that the culprits are “visitors from outer space” using the thin air at the top of the mountain as a way of acclimatising. Alan and the Prof now move things on even further by suggesting that these aliens can control zombies to do their bidding using mind control, and because they are psychic, they perceive Anne’s powers as a threat – hence the attack by Brett. “But vot vill zey try next?”

The undead Brett wakes back up, kills the hotel owner and grabs a handy meat cleaver, but is then shot dead(er) by Alan before he can do any further damage. Before anyone can think about how it is possible to stop a psychically controlled corpse with one shot to the body, someone notices that the previously static cloud is now approaching the village, and Alan suggests that they evacuate everyone up to the observatory (why? Because plot, one assumes).

But as the villagers move to safety, someone realises that a little girl has been left at the hotel. Alan returns to get her, only to come face-to-eyeball with the monsters (which, after all the build-up, is a slightly botched revelation). He manages to save the girl from their ravaging tentacles (the trick, it appears, is NOT to pick them up and wrap them around your body) and they escape to the observatory.

Sadly, at this point the plug gets pulled on any suspense / story / logic, and very quickly the besieged group realise that the monsters have a very obvious flaw, that can be exploited in the most basic way – and hilariously, by Alan and fellow bit of eye candy for the ladies Philip (Laurence Payne) taking turns (“Here, let me try!”).

Which is, to be honest, a bit of a let-down. What happened to all the mind control?

“Vell, Alan, for ze first time in weeks, the Trollenberg is free from cloud,” observes the Professor.

“And let’s hope it stays that way.”

Yes please, because one film about marauding eyeballs on top of a mountain is one film about marauding eyeballs on top of a mountain too many.