Miriam Hollowhead frantically prepares a last-minute dinner for Martin Crabneck, her husband Harry’s new boss, whom he hopes will give him a promotion at the “United Umbilical Housing Corporation.” When son, Billy, returns home with a black eye, Miriam attaches a space-age gadget to his face, and an alien creature comes out of a tube and leaches onto his eye until it is healed. Teenage son and daughter, Bud and Cindy, return home but offer their frazzled mother no help. When food delivery tubes become blocked, Miriam sends Billy and his friend, Joey, to see Stationmaster Babbleaxe at the pumping station to ask that it be repaired. She warns the boys to stay away from “the edge.” As they walk in the darkness that is their universe, Billy and Joey discuss whether or not “the edge” actually exists. The boys see the “Ream Gang,” whose job it is to clean the waste pipes. Joey taunts the workers, prompting them to chase after the two boys. When they arrive at the pumping station, Stationmaster Babbleaxe has her minion fill the liquid foodstuffs for Mrs. Hollowhead. Elsewhere, Bud leaves to play a gig with his band, while fourteen-year-old Cindy gets ready to go to a party. Her mother worries she is growing up too fast when she asks to use some “softening jelly.” Henry Hollowhead arrives with Mr. Crabneck, and the lecherous man promptly sets his sights on Miriam. Crabneck makes it clear he has no intention of promoting Henry. When Crabneck sees Cindy dressed up for the party, he lasciviously greets her. Billy and Joey return with the supplies, and Miriam finishes cooking dinner. Before leaving, Cindy feeds her invalid grandfather, who is kept in the basement, by shoving a feeding tube down his throat. She leaves with her nerdy date, Oliver Digits, whom she is using to be allowed to go to the party to meet her real crush, Jeff. Over dinner, Miriam and Billy both attempt to secure a raise for Henry, but Crabneck refuses. He makes aggressive overtures toward Miriam, saying he will consider the promotion if she sleeps with him. When Henry catches Crabneck molesting his wife in the kitchen, a fight ensues. Miriam electrocutes Crabneck with a kitchen gadget, then stabs him in the neck with a fork. He collapses, but when Billy comes near, Crabneck grabs the boy and chokes him. As the hapless Hollowheads look on, a wormlike creation emerges from a hole in the wall and strangles Crabneck. Henry strikes his boss over the head and burns him with another appliance until he finally falls dead. Henry becomes worried that he will never get his promotion, but Miriam is more concerned they will be thrown off the edge for committing murder. However, Crabneck rises, yet again, and continues his attack. Miriam stabs him in the back, and cuts off his fingers, and Crabneck, again, falls unconscious. The couple decides it would be best to murder him, but before they complete the task, there is a knock at the front door. After hiding Crabneck’s body, they are surprised to see police at the door escorting their intoxicated daughter, Cindy, home. They distract the officers, who soon leave, unaware of the hostage in the kitchen. When Crabneck crawls into the living room, Billy has the idea. The next day, the family goes to the basement to feed Grandpa, and the incapacitated Crabneck sits next to the elderly man, waiting to be fed.