X The Unknown (1956)

British Army radiation drills at a remote Scottish base attract a subterranean, radioactive entity of unknown nature that vanishes, leaving two severely radiation-burned soldiers and a “bottomless” crack in the earth. Others who meet the thing in the night suffer likewise, and with increasing severity, it seems to be able to “absorb” radiation from any source, growing bigger. Stars Dean Jagger, Edward Chapman and Leo McKern.