The Simpson family and Ned Flanders hold a s ance in the hope of communicating with the spirit of Maude Flanders. Bart tries to trick Ned by dressing up as Maude's ghost, but the real ghost of Maude, now a demonic spirit, appears instead. She asks if they're ready for tales that will shatter spines and boil blood, to which Lisa replies as "well, duh." She then pulls out a book that reads the episode's title.

Homer's hammock collapses while he is taking a nap. He purchases a new one from a passing vendor, who warns him that it carries a curse. Disregarding this, Homer lies down and discovers that the new hammock can produce clones of anyone who rests on it. He inspects the first clone and notices that it does not have a belly button.

He makes clones to do all of his chores, which include fixing a light fitting (resulting in the first clone being electrocuted to death and Homer creating a new clone to help dispose of the body), helping Marge choose an outfit, visiting Grampa, and play baseball with Bart, Lisa and Maggie. He also discovers that the clones are becoming increasingly less intelligent. When one clone kills Ned Flanders, Homer decides to get rid of the clones and the hammock. He bundles the clones in a truck and takes them to an isolated cornfield, where he abandons them, along with the hammock.

The clones use the abandoned hammock to make an army of Homer clones, which wreak havoc in Springfield. US army officials gather in the Mayor's War Room and determine that the clones will eat up America by the next day. Lisa suggests that a fleet of helicopters lure the clones into Springfield Gorge to their deaths by using giant donuts as bait. The plan works, and the clones tumble into the gorge in pursuit of the donuts. That evening, Marge is shocked to find that the Homer in bed with her is actually a clone, the real Homer having actually been the first one to jump off the cliff with the other clones. Marge is distressed by the real Homer's death until the clone Homer soothes her with a backrub.

While at the Springfield Cemetery mourning the loss of her pet goldfish, Lisa inadvertently discovers the grave of William H. Bonney, a man who was killed in his youth by gun violence. According to his epitaph, he "dreamed of a world without guns." In his memory, Lisa starts a gun control crusade, which makes Springfield 100% gun-free; even the police no longer possess guns. The town is now defenseless, causing the corpses of Bonney, in reality notorious outlaw Billy the Kid, and his "Hole-in-the-Ground" gang Frank and Jesse James, the Sundance Kid, and Kaiser Wilhelm II to rise from the dead. The gang wreaks havoc on the town until Professor Frink invents a time machine, which Homer uses to go back in time to stop the gun ban and destroy the zombies. Homer tells the citizens of Springfield to shoot at the zombies' graves, causing them to rise up and flee. Lisa feels guilty about banning guns, concluding that sometimes they are the answer. A futuristic Homer suddenly appears to warn them about guns that have destroyed Earth in the future, only to be shot by Moe, who is fed up with all the contradictory messages. Moe then commandeers Frink's time machine to find some "caveman hookers".

The Simpsons visit "The Island of Lost Souls," where they find Dr. Hibbert running the island's resort after hearing rumors he has gone mad. The family has dinner with Professor Frink, who is transformed into a turkey as the main course. When Marge explores the island, she is captured by Hibbert, who transforms her into a blue panther. She returns to her room and has violent, animal sex with Homer, who belatedly realizes that she has been mutated.

Homer treks across the island looking for a cure to Marge's condition, but encounters Ned Flanders, who is now a cow-human hybrid in need of a milking. After Homer reluctantly milks him, Ned takes him to meet other Springfield inhabitants who have also been turned into mutant animals, including Bart (now a spider), Lisa (now an eagle) and Maggie (now an anteater, who is nearly eaten by Lisa until Homer intervenes). Homer, initially appalled at what everyone has become, eventually embraces the concept of being a mutant animal upon realizing how well it fits in with his personal lifestyle. The segment ends with a mutated Homer in the form of a walrus and the rest of the Simpsons and Springfield mutants lounging aside the resort's pool, intending to spend the rest of their days on Hibbert's resort.

Meanwhile, the two aliens Kang and Kodos comment on how the skull-shaped island looks like their alien number four.