Plot
A meteorite crashes near Arborville, California. An elderly vagabond discovers within a sphere a massive slime mold-like substance that adheres to his hand. Three high school students—football star Paul, cheerleader Meg, and outsider Brian—take him to a hospital. After Brian leaves, Paul witnesses the lower half of the rescued man melting from exposure to the Blob. As he calls for help, the Blob drops on top of him. Meg returns to find Paul being consumed by the growing Blob. It fully dissolves him and seeps out of the hospital.
After Brian and Meg have unsatisfactory encounters with the police, they meet at a diner where Meg tells Brian about the Blob. Brian's disbelief shatters when the diner's handyman George is fatally pulled into the sink's drain. The growing creature pursues them to the diner's walk-in freezer but retreats upon entering. After consuming the diner's owner, as well as Sheriff Geller, the Blob reenters the sewers. Meg and Brian return to the police station, where the dispatcher tells them that Deputy Briggs is near the meteor landing site. They discover a military operation led by scientist Dr. Meddows, who orders the town and the two teens quarantined. As Brian escapes, Meg is taken to town, where she learns that her younger brother Kevin snuck into the movie theater with his friend Eddie. The Blob enters the theater, killing several staff and audience members. Meg rescues Eddie and Kevin as audience members flee the theater.
Brian learns that the Blob is a biological warfare experiment created during the Cold War. It became so dangerous to handle that it was launched into space in a satellite. It instead continued to feed off of bacteria mutated by space radiation, growing big enough to crash the satellite back to Earth. Brian evades government personnel by riding his motorcycle into the sewers. Meg and Kevin flee from the Blob, but Eddie is consumed. Kevin escapes by scaling a pipe to the surface. The Blob is distracted by government agents searching the sewers as Meg meets back up with Brian. Meddows orders the sewers quarantined, however Brian uses a surviving agent's grenade launcher to blow open a manhole and publicly confront Meddows. The community begins to turn on Meddows, however he claims Brian is infected and dangerous. He attempts to execute Brian himself, only to be dragged into the sewers by the Blob. The military attempts to blow it up with grenades and other explosives, but only succeed in enraging the creature; it bursts from the sewers and feasts on the population. Reverend Meeker proclaims the scene to be the prophesied end of the world, after a failed flamethrower attack sets him ablaze. Meg saves him with a fire extinguisher inadvertently hitting the Blob with the extinguisher gas. When the creature recoils, she realizes that it cannot tolerate cold.
The survivors retreat to the town hall and hold the Blob off with furniture-barricades and fire extinguishers, but it is a losing battle; it engulfs half the building and devours Briggs. Brian goes to the town's garage and gets a snowmaking truck that has canisters of liquid nitrogen attached. As the Blob is about to consume Meg and her family, Brian shoots snow at it. Angered, the Blob turns its attention toward him and knocks the truck over in retaliation, trapping Brian. Meg lures the Blob away from Brian toward the canisters she has rigged with an explosive charge taken from a dying soldier. The Blob is about to overrun both Brian and Meg when the charge goes off, blowing up the canisters and covering the Blob in liquid nitrogen, flash-freezing it. Moss Woodley stores the Blob's crystallized remains in the town icehouse.
Sometime later, at a tent revival church service in a field, Meeker, disfigured by his burns and driven insane, preaches a doomsday sermon. After the service in his private quarters, one of his congregation asks when the day of reckoning will come. Meeker simply replies, "Soon." He then secretly holds up a glass jar containing a still living and trapped piece of the Blob, cryptically saying "The Lord will give me a sign."
