 A meteorite falls in the country of a small town, bringing a jelly creature. An old farmer is attacked by the alien in his hand, and the youths Steve Andrews (Steve McQueen) and his girlfriend Jane Martin (Aneta Corsaut) take him to Dr. T. Hallen (Steven Chase). The local doctor treats carefully the blister, and asks Steve to investigate the location where they found the old man. When Steve returns, he sees the blob killing the doctor. Steve and Jane try to warn the police and the dwellers, but nobody believe on them, while the blob engulfs many people, getting bigger and bigger.