The film opens with work being done at Hobb's End, a fictional station on the London Underground's Central line. When skulls are uncovered by the workers, Dr Roney (James Donald) is called in to investigate. That's not all they found - an alien spacecraft is found buried beneath the mud, bringing Colonel Breen (Julian Glover) and Professor Quatermass (Andrew Kier) into the story as rocket experts who need to decide exactly what the spacecraft is. Soon Quatermass and Roney's assistant Miss Judd (Barbara Shelley) have uncovered local tales of demons and poltergeists, and the site has a long history of disturbances. When the corpses of giant insects are found inside the craft, Quatermass begins to wonder if these aliens and the skulls found in the pit are connected.
It's an interesting plot, and the hypothesis that alien intervention may explain the sudden evolution of man from apes is more plausible than most. Quatermass goes one step further to guess that maybe the likes of poltergeists and telekinesis can be explained by their alien ancestry - maybe humans were originally part Martian. It all kicks off and soon London is tearing itself apart. One of its attractions is definitely the idea of something buried under London - I know I've always been fascinated as much by what is below London as what is on display at street level. With forgotten or abandoned stations, plague pits and buried Roman amphitheatres, it almost seems plausible that a Martian spaceship could be down there as well.
I know some people have problems with the Quatermass films, and many prefer the BBC TV serial, but I've never seen it so I can't really compare it. All I have to go on is the films, and in a way, it's amazing how much Quatermass & The Pit prefigures more modern cinematic tropes. Quatermass was looking at the links between humans and aliens well before The X Files came along, and the shots of Londoners facing off in the streets recall later zombie films; those Londoners who still possess alien ancestry hunt those who don't, seeking to destroy anything which doesn't belong to the alien colony. Sound familiar?
I can't help thinking that one of Hammer's problems was that by the late 1960s, its period horrors were beginning to look rather quaint and dated compared to the output of other filmmakers. A year after Quatermass & The Pit, both Rosemary's Baby and Night of the Living Dead introduced horror into the modern day, and brought it kicking and screaming into the home. It took Hammer until 1972 to bring Dracula into the present day, and even then, it seemed way out of date. By contrast, Quatermass & The Pit represented a possible direction that would have allowed Hammer to blend science fiction with horror within contemporary settings - and hopefully find audiences.
Anyway, here's the opening scene...