X, the Unknown is one of the earliest Hammer horror films, made before their forays into Frankenstein and Dracula remakes, and having more in common with their Quartermass sci-fi films. Its oozing blob monster is a little too slow moving to be truly terrifying, but the film has tension, a fairly logical script and an interesting scientist in Dean Jagger, far less confident of victory against the unknown than Brian Donlevy's Quartermass. William K. Everson