In a small Pennsylvania town in July 1957, teenager Steve Andrews and his girlfriend Jane Martin kiss at a lovers' lane when they see a meteorite crash beyond the next hill. Steve goes looking for it but Barney, an old man living nearby, finds it first. When he pokes the meteorite with a stick, it breaks open and a small jelly-like globule blob inside attaches itself to his hand. In pain and unable to scrape or shake it loose, Barney runs onto the road, where he is nearly struck by Steve's car. Steve and Jane take him to Doctor Hallen. Doctor Hallen anesthetizes the man and sends Steve and Jane back to locate the impact site and gather information. Hallen decides he must amputate the man's arm since it is being phagocytosed. Before he can, the Blob completely absorbs Barney, then Hallen's nurse Kate, and finally the doctor himself, growing redder and larger with each victim.