THE DEADLY SPAWN

Two campers are nearby when a meteor falls to Earth. When they investigate, they are attacked and eaten by a lifeform that emerges from the crashed rock.

A house near the crash site is the home of Sam and Barb, who are set to venture out of town, and their two children, college student and budding scientist Pete and his younger brother Charles, a monster movie fan. When a rainstorm sets in, Sam goes downstairs to check the basement for flooding and is eaten by the bizarre monstrosity. Barb suffers the same fate when she goes looking for him. Visiting are Aunt Millie and Uncle Herb, who think Sam and Barb have left for their trip.

Pete sets up a study date with classmates Ellen, Frankie, and Kathy. Uncle Herb, a psychologist, and also preparing for a conference, wants to investigate Charles' interest in the macabre, and he holds a brief session with the boy before he falls asleep in the living room. Aunt Millie heads over to her mother Bunny's house for a luncheon with her retired friends. When an electrician arrives to investigate a circuit breaker malfunction in the basement, Charles dons a costume and goes down to scare him. There, he discovers the basement is infested with slug-like creatures feasting on the electrician's and his mother's remains, guarded by their huge mother, the monster from the meteor crash. After realizing that the eyeless creatures react to sound, he stands silently, escaping his parents' fate.

Meanwhile, Ellen and Frankie have discovered one of the tadpole creatures dead on the way over to the house, and deem it unlike any animal on Earth when they dissect it. Frankie hypothesizes that the creature could be from outer space, but the hard-nosed Pete dismisses that theory. At Bunny's house, Millie arrives and they prepare the luncheon, unaware that the spawn have infested the house. When her guests arrive, the spawn creatures emerge and attack them. The women fight back and manage to escape in Millie's car.

Back at the house, Pete, Ellen and Frankie seek out Uncle Herb to get his opinion on the creatures, only to find him being devoured by the spawn. As the adult creature emerges and charges them, they run upstairs to barricade themselves in Charles's bedroom. Charles distracts the adult by turning on a radio, which it eats, causing an electrical fire which burns it. Pete and the others then see Kathy arriving and pull her into the bedroom just in time to save her from the beast. The teens decide to head for Pete's bedroom, where there is a phone to call for help, but as they emerge, the adult creature pounces on them. Pete flees to another room and from there onto the roof; Frankie and Kathy run up to the attic, while Ellen stays in Charles' room. The creature breaks down the door, bites Ellen's head off and throws her body out the window. Pete returns through the attic window; but traumatized after seeing Ellen's body as well as his parents' car, the latter signaling to him they never left for their trip, he becomes unhinged, fighting with Frankie to open the attic door, which attracts the creature.

Meanwhile, Charles has concocted a plan: he has filled a prop head with explosive flash powder, with a frayed electrical cord trailing behind to act as a fuse. He arrives in the attic before the creature can attack Pete and the others, spurring the creature into devouring the prop head. However, the cord proves too short to plug into an outlet. One of the spawn creatures appears and attacks Charles, but gets in the way of the adult when it lunges at Charles and ends up being eaten. Now that the monster is distracted and its mouth close enough, Charles manages to get to the outlet, igniting the powder and blowing up the adult.

With the threat revealed, a massive hunt is mobilized. Policemen and townspeople go around killing the alien spawn and burning the remains. Millie returns to the house to care for Pete and Charles as best she can, while we see Frankie and Kathy sitting in the back of a police vehicle. Pete, very catatonic, is put into an ambulance. Millie and Charles leave with some officers in the back of a police car. That night, a lone patrolman stands guard outside the house. His contact on the CB radio is confident that the spawn has been wiped out, but then the patrolman hears a low rumbling, and sees the hill by the house lift up, revealing a fully-grown spawn of colossal size.

The surviving teenagers use sound to distract the alien, causing it to eat a radio and catch fire, but as they try to escape, the creature attacks again and claims more victims.

The film ends with a partial victory: while the teens temporarily outsmart the alien using its sensitivity to sound, the threat remains lethal and persistent, underlining the relentless nature of the alien menace. This ending leaves the fate of the survivors precarious and suggests that the danger may not be entirely vanquished, true to the film’s grim, grindhouse spirit.