What with the success of the first Quatermass serial and film, plus the sequel serial airing on the BBC after the first film, author Nigel Kneale found himself with a bit more clout, something Hammer used when they did a film version of the second sequel.
Professor Quartermass (Brian Donlevy) is trying to drum up support for his moon colonization plans when a car narrowly avoids hitting him. Racing to the wreck, the woman inside the car explains her boyfriend is going into some kind of shock after his face was burned by a strange rock he found. He helps the couple and takes a few pieces of the stone with him.
Back at the British Rocket Group's HQ, scientists Brand (William Franklyn) and Marsh (Bryan Forbes) are having an odd moment. The radar is showing scores of meteorites in the sky, but they're traveling far too slow. In fact they seem to be landing. Quartermass is intrigued. He leaves the rock samples and heads towards the supposed landing site. He and Marsh hit the road, and what do they find?
A near exact copy of Quartermass's proposed lunar colony. The same colony the government said was too expensive to build or develop. The two men find scores of stones laying around, but when Marsh picks one up, the stone breaks open and sprays his face with a hot gas, as well as shooting something into his cheek.
Armed men appear, but they seem more concerned with taking Marsh away rather than helping him. When the locals are less than helpful, Quartermass hightails it to London where he asks Inspector Lomax (John Longden) for help. All Lomax knows is that the project is supposed to be something to do with synthetic food and that it is extremely top secret. Lomax does point Quartermass towards MP Vinnie Broadhead (Tom Chatto), who wants to know what the government has been spending its money on for the last two years. Quartermass is in luck, as Broadhead was finally cleared for a security pass and the MP takes Quartrmass with him when he does an inspection on the plant.
The visit is odd. The plant PR officer (John Van Eyssen) is utterly unhelpful and seems to be going out of his way to be rude. Quartermass and Broadhead slip away, going through the infirmary. This makes Quartermass suspicious. Where's Marsh? In fact the whole hospital wing looks pristine. Broadhead conducts his own inspection near one of the giant domes dotting the planet. It's supposed to be a storage vat for the food, but when Broadhead pops open a panel, he's overcome by toxic fumes and falls inside.
He crawls out, covered in thick black sludge. He doesn't live long afterward. Quartermass manages to escape and warn Lomax, but the papers next day swear Broadhead has gone on a fact finding mission overseas. When Lomax takes the matter to his supervisor, he notices the man has a scar like the PR man. The two head back to the plant, with journalist Jimmy Hall (Sid James) in tow. The trio manages to find that food is being produced...but not food fit for human or indeed, anything of Earth. Can Quartermass stop this alien menace before its too late?
Darn good, and sort of a precursor to Invasion of the Body Snatchers. Honestly, Quartermass has more problems with the local people than with the aliens.