“Let’s not conjure up visions of nameless horrors creeping around in the night…”

It’s the 1950s, and with the UK still in the grip of rationing, the army is pressed into service to hunt for tins of spam growing in its natural habitat (muddy fields, in case you didn’t know).

Spam is number one, but coming up fast in the list of things 1950s people can’t get enough of is radiation. Whether they’re the soldiers practising with “a lump of harmless radioactive material” or eminent doctors cocking around with Meccano and cobalt in their shed, it must have been on everyone’s Christmas list in 1956.

Seems like they all need a reminder of how dangerous radiation can be, so it’s frankly a good thing that as Corporal Lansing (Kenneth Cope) continues his spam-detection activities (not really, he’s testing out a Geiger counter) he prompts an earthquake and massive explosion.

Dr Royston (he of the Meccano set) is sent from the nearby nuclear facility to check out what the what the army have found – but the big crack (please, we’re better than that) that appeared in front of the soldiers is now devoid of radioactivity – unlike the soldiers themselves, who have been subjected to massive burns. The crack is huge, incredibly deep, and clearly very dangerous (cf. soldiers burned to death when it appeared) – so exercising the full vigour of 1950s health and safety, they rope it off and leave it unobserved overnight.

Bad move to leave it unobserved. Later that night, two young Scots lads (did I mention we’re in Scotland? We’re in Scotland) are out on a dare to investigated a nearby “haunted” tower, when one gets more than he bargained for (or perhaps exactly what he bargained for) when he’s menaced by an unseen, crackling thing.

Dr Royston (Dean Jagger) sets off to investigate the tower, but only finds a drunken Scots bloke, his illegal whisky still – and one of Royston’s “highly dangerous” (all of a sudden) radioactive samples, now actually devoid of any radioactivity. As is his laboratory when he returns to it, which has been broken into, and all radioactivity “sucked out” by something. Because of the crime, rumpled Inspector “Mac” McGill (Leo McKern) is sent up to Scotland to investigate by the powers-that-be, immediately striking up a relationship with Royston.

The boy is now also dead, prompting an attack by his father on the innocent Dr Royston, who, he claims, is not a doctor of medicine, he just creates bombs! (Oppenheimer, much?)

But as we all know, there’s actually nothing sexier than radiation, and what girl could resist a date in the “radiation room”? Not Zena, anyway, a nurse who meets up with a randy orderly for a swiftly curtailed bit of nookie. Curtailed when a crackling, face-melting thingy turns up.

All this leads Dr Royston to embark on a huge amount of plot exposition, pretending to be “science”, as he suggests that whatever this thing is, it can take any form it wants to. Apparently “energy needs energy”, and his ramshackle explanation continues, ending with “I’m just putting forward the theory based on the facts that we know” (No, you’re not).

Just in case this hadn’t got the plot moving enough to keep the film down to sub-89 minutes, his next science-y suggestion is for someone to be lowered into the fissure that whatever it is came out of, on a rope, with no actual protective gear on at all. Because if you remember earlier, radioactivity is perfectly harmless apart from when it isn’t. Besides which, if there’s any radioactivity on the Geiger counter the poor unfortunate is carrying, he’s to let the people on the other end of the rope know, and they’ll get him out of there quickly. Phew, for a minute there I thought they hadn’t thought this through.

On being lowered into the fissure, Royston’s assistant Peter (William Lucas) finds some gooey dead bodies, then his Geiger counter starts going nuts (“Get me out of here! Get me out of here quick!”)

The soldiers give him a quick tug and he comes up pretty quickly, unharmed but babbling: “I don’t know what it was. It was like something out of a nightmare. It was horrible!”

That’s enough for the practical army, and it’s time for the enormous crack to get a heavy dose of Polyfilla.

Now aware that what they’re dealing with is some kind of living mud (“How do you kill mud?”), as luck would have it Dr Royston’s Meccano set might just hold the answer to how it could be stopped. And just in time, too – the concreting-over hasn’t worked, the police are getting calls about melted villagers, and the ever-growing thing is on its way to the nearby nuclear facility… which is on the other side of the village.

I’m not going to lie, X The Unknown is better before you see the monster. But on the way there are some genuinely nasty moments and scenes like the lowering into the fissure, which joking aside works remarkably well.

I’m not entirely sure the advice given to the public once the monster is on the rampage is particularly well thought through (Stay indoors – and upstairs, if possible! We know it’s going to head straight past the church – everyone go to the church!), but we saw worse in real life in 2020 (Ithankyew)…