Professor Bernard Quatermass , an interplanetary research scientist, is returning to his observatory when his car is almost hit by a vehicle carrying a young man mysteriously injured by a strange object which fell from the sky. On closer examination, Quatermass learns the incident occurred earlier on a desolate moorland. He retains fragments of the object and continues his journey after taking the man to hospital.
At the observatory Brand, his chief assistant, has observed the objects falling on his radar screen. Brand estimates the missiles are falling about ninety miles away - at Winnerden Flats. Analysis proves the object is symmetrical and formed of a substance unclassified on this planet.
Quatermass decides to visit Winnerden Flats and together with Marsh, one of his assistants, he sets off by road. On their arrival, they are amazed to discover a mysterious research plant similar in design to "moon project", a model upon which they have been working - a project for experimenting with the possibility of creating an artificial atmosphere on the moon. Their excitement increases when Marsh finds a complete specimen, but it breaks up in his hands and something from within settles on his face. He slumps to the ground disfigured by a mysterious mark.
Before Quatermass can help his stricken friend he is surrounded by armed security guards clad in black uniforms. They take Marsh to the plant and when Quatermass protests, he is clubbed and ordered to go.
Reluctantly he does so, but only a few miles to a prefabricated town used to house workers from the plant. Here he tries to get police assistance, but is informed there are none - merely a local "camp committee". Quatermass interviews the secretary but with no satisfaction. He drives to Frawley, fifteen miles away and contacts the police. They claim the plant is a top government secret and offer no assistance.
Dissatisfied, he returns to the observatory and early next morning drives to London to see his friend inspector Lomax of Scotland Yard. He relates the whole story and Lomax informs the plant is producing synthetic food. Quatermass will not accept this and asks permission to visit it officially. Lomax puts him in touch with Vincent Broadhead MP, who is also curious about the purpose of the plant. Broadhead helps Quatermass to join a special group on a tour of inspection.
On their arrival at the plant all seems quite normal. In trying to find Marsh, however, Quatermass and Broadhead clash with officials. Broadhead is killed, and with the exception of the scientist, the party is apprehended. Quatermass escapes with definite evidence of the plant's real purpose. Back in London he acquaints Lomax with the latest developments. However, their efforts to get the authorities to act are thwarted and they decide instead to enlist the aid of Jimmy Hall an ace crime reporter, to publicise the plant in his newspaper.
Together Quatermass, Lomax and hall return to the prefabricated town near Winnerden Flats and interview some of the workers. Their talk is interrupted by the descent of another missile which crashes through the roof and kills one of the company. Before they can act, the armed security guards arrive and their callous attitude towards the victim enrages the workers.
Accompanied by Quatermass and Lomax, the workers, in a rebellious mood, break into the plant and the final battle with the intruders from another world begins.
Plot summary from the British Quatermass 2 press book, 1957.