X the Unknown (Sol Lesser Productions, Exclusive Films, Hammer Films, Warner Bros., 1956)

by Mark Gabrish Conlan • Copyright © 2026 by Mark Gabrish Conlan • All rights reserved

Last night (Wednesday, May 7) I showed my husband Charles a film I’d got in the same container as Four Sided Triangle: X the Unknown (the official poster had a three-dot ellipsis between “X” and “the,” but the film’s own opening credits did not), a strange little story by future Hammer director Jimmy Sangster about a menace, not from outer space this time, but from inside the Earth’s crust. As explained in the exposition by Dr. Adam Royston (Dean Jagger, an American actor imported to star in the film by producer Sol Lesser, a long-time Hollywood bottom-feeder who got his name on the copyright), as the earth’s crust expanded and took up more of the volume of the planet, agencies inside the crust started feeling squeezed and eventually rebelled, breaking open the crust in certain places to grab the energy they needed as their source of food. (Some critics at the time praised Sangster’s script as at least not being yet another tale of an alien invasion from outer space.) The film is set in Scotland, where the British army is doing tests to train their troops in the proper use of Geiger counters to detect underground radiation, only one of the servicemembers detects radiation in a location other than where the atomic materials have been planted as part of the exercise. The army orders the suspicious site cordoned off, but two young boys, Ian Osborn (Fraser Hines) and Willie Harding (Michael Brooks), investigate the site on a dare. Ian emerges unscathed but Willie is badly burned and eventually dies in the hospital of his wounds, much to the understandable displeasure of his parents Jack (Jameson Clark) and Vi (Jane Aird). Later the great whatsit kills a doctor in the hospital where the boy was being treated (when we saw his flesh literally melt on screen I joked to Charles, “Now this looks like a Hammer movie”). It also opens a deep fissure in the ground and kills two soldiers stationed outside the perimeter to guard it. Royston’s colleague Peter Elliott (William Lucas) volunteers to be lowered into the fissure to investigate it first-hand, taking a Geiger counter with him and saying he’ll asked to be raised out of the pit immediately once it starts registering radiation. He gets his (and our) first clue about the mysterious menace when an oddly animate patch of mud fastens itself to his hand. Royston and Elliott have a frosty relationship with Inspector “Mac” McGill (Leo McKern, who later played Clang, the High Priest of Kalili, in Help! and thus put the rest of the cast one degree of separation from The Beatles) of the local police. The cops insist on trying to blow up the monster while Royston says that it feeds on energy and therefore supplying it with more energy will only help it.

Ultimately the mud-monster emerges from its cave and starts menacing everyone in the vicinity in search of the radioactive cobalt core from a nearby nuclear reactor, which coincidentally has been removed as part of a shutdown of the reactor instituted by Royston. The scientists finally figure out a way to kill the thing using the cobalt core as a lure, on the theory that by bombarding it with out-of-synch radio waves they can neutralize it and keep it from feeding on the surrounding energy. Just as the scientists think they have killed it with their first explosion, it explodes a second time, leaving it uncertain at the film’s rather abrupt ending if they’ve really killed the whatsit or just put it to sleep for a while. I remembered that both Charles and I had seen this movie before because I’d joked about a sequel to it and even come up with a title: X2: Killer Mud Strikes Again! According to the film’s Wikipedia page, the originally assigned director was American expatriate and blacklist victim Joseph Losey, but he was let go when Dean Jagger refused to work with him, probably fearful for his own future if he made a film with a blacklisted director like Losey. Instead they assigned the film to Leslie Norman, best known as a comedy director for Ealing Studios and rather out of place in a science-fiction/horror film. The page also says that Sol Lesser had a deal to release the film in the U.S. through RKO, but at the time that studio was in its death throes during the three-year interregnum between Howard Hughes’s selling it in 1955 and its eventual closure three years later. During that time RKO seemed to be going through a corporate version of post-traumatic stress disorder, and by the time its owners bowed to the inevitable in 1958 they’d begun placing their unreleased films with other studios, mainly Warner Bros. and Columbia. X the Unknown ended up at Warners, which released it on a double bill with Hammer’s first foray into classical monster-movie making, The Curse of Frankenstein (1957). The page also explains that Hammer’s producer, Anthony Hinds, had originally wanted to call Dean Jagger’s character “Bernard Quatermass,” but the creator of the Quatermass character, Nigel Kneale, refused to give permission. There’s at least one other quirky credit in the film besides Leo McKern’s: Anthony Newley appears briefly as one of the servicemembers killed by the monster early on in the Hammer equivalent of a Star Trek “red shirt.” X the Unknown is an O.K. entry into the alien-monster sweepstakes, surprisingly dull for most of its running time (for which I’m inclined to blame Sangster rather than Norman) and with a woefully unscary monster. It’s basically the same concept as The Blob, made in the U.S. two years later, but The Blob, while no great shakes as a movie either, at least was made with a cheery awareness of its camp aspects that pretty much eluded the makers of X the Unknown.