In Abbeville, a small mountain town, Paul Taylor, a high school football player, asks cheerleader Meg Penny for a date. At the diner, Sheriff Herb Geller asks Fran Hewitt, the owner, for a date after she gets off work. In the mountains, rebellious teenager Brian Flagg speeds his motorcycle to jump a collapsed bridge at Elkin’s Grove. The bike falters and Brian slides into the ravine, to the delight of “Can Man,” a recluse collecting cans. Brian goes to Moss Garage and asks Moss Woolsey to lend ratchets to fix Brian’s motorcycle. In return, Brian offers to help fix the snow-making vehicle for the local ski resort. Later, Can Man sees a glowing object crash, pokes the gel oozing out of the wreck and a blob covers his hand. Before Meg leaves for her date with Paul, her brother Kevin and his friend, Eddie Beckner, reveal they are sneaking into a horror movie later. However, Mrs. Penny insists Kevin cannot see the movie. In Elkin’s Grove, as Brian fixes his motorcycle, Can Man runs toward him, screaming. The old man chops his own wrist with an axe, but the blob moves over the wound. Can Man runs onto the road in front of Paul’s car and is hit. Paul and Meg place the man in their car, and insist Brian accompany them to explain what happened. At the hospital, the receptionist admits Can Man to a room and orders Paul to complete paperwork. Disgusted by the hospital’s lack of concern, Brian leaves. Paul heads for a vending machine and sees the blob rippling through the old man’s body. He runs for the doctor and when they return, the lower half of Can Man’s body is gone. As Paul calls Sheriff Geller, the blob drops from the ceiling onto him. Meg hears Paul’s screams and runs into the room. Paul screams from inside the blob as it absorbs his body and Meg faints. Later, Sheriff Geller, Deputy Bill Briggs, and her parents think Meg is in shock and do not believe her story. The Highway Patrol arrives with Brian, and Briggs thinks they have the culprit. The blob absorbs a couple parked nearby and heads for town. At the police station, Sheriff Geller releases Brian, noting he has no blood on him and no motive. Meg sneaks out of her house and arrives as Brian leaves jail. She follows him to the diner which is closing for the night, but Fran offers to make them sandwiches. Meg tells Brian that the blob killed Paul and is getting bigger. Sheriff Geller sends Deputy Briggs and several volunteers to search the mountain, and heads to the diner to meet Fran. In the diner kitchen, the cook tries to unclog the sink and the blob attacks him. Fran, Brian and Meg rush into the kitchen as the blob sucks the man’s body into the drain pipes. The blob explodes from the sink, and Brian and Meg run into the freezer. The blob slips under the door, but is repelled by the cold and leaves several frozen blob bits on the icy floor before slithering out. Moments later, Brian and Meg sneak out of the diner. Fran jumps out the kitchen window, runs down the alley and calls the sheriff from a pay telephone. As she learns Sheriff Geller is headed in her direction, the blob surrounds the pay phone. Fran sees Geller’s dissolving face inside the blob before it absorbs her. Reverend Meeker sees the blob slide into the sewer system. He rushes to the diner, finds the hardened blob pieces in the freezer and places a piece inside a jar. At the police station, the receptionist tells Brian and Meg that Deputy Briggs is at Elkin’s Grove. When the teens near the crash site, they are surrounded by men in “Haz-mat” protective suits and meet Dr. Meddows, who claims to be the head of a government-sanctioned biological containment team. He informs them that a meteorite carrying a killer gene crashed in Elkin’s Grove and the entire town is under quarantine. Brian wants to retrieve his motorcycle, but he and Meg are forced into a locked van. En route to town, Brian unlocks the back door, but Meg refuses to escape with him, insisting she has to help her family. Meg arrives at the town hall and reunites with her parents. They find Eddie’s mother and learn the boys went to the horror movie. Meg sneaks away from the soldiers and runs to find her brother. At the theater, the blob enters the projection room through an air conditioning vent and kills the projectionist and manager before oozing into the theater. Meg runs inside as frightened patrons flee. She finds Kevin and Eddie at the rear exit and they run into a dead-end alley. When the blob explodes from the building, Meg lifts a sewer grate and they drop into it, replacing the grate before the blob reaches them. Meanwhile, Brian retrieves his motorcycle at Elkin’s Grove and watches Meddow’s team raise the “meteorite,” which is actually a government capsule carrying an experimental bacteria that mutated in space. Meddows proclaims his experiment is the greatest breakthrough in weapons research. Another scientist warns that the blob is growing too fast and could wipe out the United States within a week, however Meddows dismisses his claim and insists the blob can be contained. They learn the blob is in the sewer system with Meg and the two boys. Meddows wants the blob secured in the sewer and declares the humans are expendable. A soldier discovers Brian, but he hops on his motorcycle and speeds away. They chase Brian to the rotted bridge where he jumps his motorcycle over the ravine. Brian speeds into a large sewer drain and rides inside. In town, three soldiers enter the sewer system near Meg and the boys, who slog through water toward an overhead grated sewer opening. The blob appears in the water and they run to the ladder. As they climb toward the grate, the blob grabs Eddie and pulls him underwater. Meg dives to save him, but Eddie is dead. Meg follows her brother to the opening, but it is too small for her. The soldiers shoot the blob and it turns toward them. Meg tells Kevin to run to the town hall, then falls back into the water and heads for a shaft to a higher level. When she nears the top, Brian arrives on his motorcycle and they race off as the huge blob bursts into the tunnel. They crash further down the tunnel and encounter the surviving soldier. They follow him to a manhole. Meddows sees them below, but closes the manhole and drives a truck over it to prevent their escape. Brian notices the wounded soldier has a grenade launcher, and he shoots it up the shaft, blowing the manhole open and exploding the van. Meg and Brian climb through the opening and Brian grabs a rifle as soldiers aim weapons at the couple. Meddows screams that Brian is infected and will spread the plague, but Brian tells the truth. Meddows aims at Brian, but the blob kills him and pulls his body into the sewer. Everyone shoots at the blob and a soldier tosses a bomb into the sewer, causing an explosion. The ground beneath them shakes and the enormous blob explodes through the street and attacks panicked citizens. Reverend Meeker walks toward the blob, proclaiming this has been prophesied. A soldier fires a flame thrower, but the blob is unaffected and Meeker catches fire. Meg gets a fire extinguisher and douses Meeker’s flames. A blob tentacle grasps for her but recoils when Meg blasts it with the fire extinguisher. Realizing the blob cannot stand cold, Meg and the townspeople grab fire extinguishers and start spraying. Brian runs to Moss Garage for the snow-making machine and aims the snow at the blob. Meg plants explosives on the vehicle’s liquid nitrogen tanks and the blob is frozen in the resulting snowfall. Townspeople rush to get the crystallized blob pieces to the icehouse before sunrise. Later, the burned, crazed Reverend Meeker preaches in a tent about judgement day. After his sermon, a congregant asks when the day of reckoning is coming. He promises the Lord will give him a sign and holds up his jar with a living blob fragment inside.