The camera zooms into a graveyard showing various tombstones and then the Simpsons home and the Simpsons break the floor and sit on the couch as zombies. Later Bart is seen walking around a room with paintings in light of Rod Serling's Night Gallery and tries to introduce the show, but Marge and Maggie interrupt telling Bart to tell the viewers that the show is scary and might prefer to listen to the old The War of the Worlds broadcast on the radio instead but Bart ignores and they watch the first part.
In a parody of The Devil and Daniel Webster, Homer falls asleep at work, dreaming of donuts. When he wakes up to get one to eat, however, he finds out from Lenny and Carl that the remaining donuts have already been eaten. Homer then declares that he'd sell his soul for a donut, causing the Devil (in the form of Ned Flanders) to appear. After signing a contract, Homer is given his donut, with the provision that as soon as it's finished, the Devil will own his soul. However, Homer finds a loophole: if he doesn't finish the donut, he's safe. Homer openly mocks this loophole, to which the Devil promises that he will go to Hell eventually. One evening, Homer goes down to the kitchen, and without realizing it, eats the final bite of the donut. As expected, the Devil comes to take Homer's soul, but Lisa asks him to hold a trial, which the Devil agrees to hold a trial at the stroke of twelve midnight. However, Homer must spend the day in Hell being severely tortured until the trial. Aside from being chopped into pieces, the Blue Demon in the Ironic Punishment Division laughingly plans to feed Homer all of the donuts in the world (this plan backfires when Homer gleefully keeps eating, much to the confusion of the demon). Back on Earth, Marge already has the trial area set up and hires Lionel Hutz to defend Homer. The Devil and Hutz barter on specific terms before the trial begins. The Devil agrees to Hutz's request for bathroom breaks every half hour, and Hutz agrees that the Devil can choose the jury, serving as a reference to Jabez Stone, a fictional character who also sells his soul. The Devil's jury includes Benedict Arnold, Lizzy Borden, Richard Nixon (who was actually still alive at the time), John Wilkes Booth, Blackbeard the Pirate, John Herbert Dillinger, and the starting line-up of the 1976 Philadelphia Flyers. The Devil gives the evidence of the contract Homer signed, pledging his soul for a donut. Lionel Hutz counters with the definition of a contract according to the dictionary, stating it as something that is unbreakable. Realizing that he's put his foot in his mouth, Hutz asks to be excused to use the bathroom. When he doesn't return immediately, Marge finds the bathroom window open and Lionel Hutz Is long gone.
As the judge prepares to sentence Homer for eternity of death, Marge shows the jury a photo album showing their wedding day, where Homer's eating of the whole wedding cake sent them to the emergency room. On the back of a photograph, it is revealed that in a statement of love to Marge, Homer pledged his soul to her. This causes the jury to declare Homer's deal with the Devil to be revoked. However, the Devil is not willing to let Homer best him, and turns Homer's head into a donut.
The next morning, Homer can't stop eating parts of his head. As he decides to go to work, Lisa cautions him to stay home because standing outside the house are the Springfield Police Department, waiting to rip apart his donut-made head and enjoy it with their morning coffee.
Back in the art gallery, Bart narrates the second spooky story. In a parody of the Twilight Zone episode, Nightmare at 20,000 Feet, Bart has a nightmare where the bus crashes and wakes up very paranoid. Bart and Lisa then get on the bus on one rainy morning with Principal Skinner on the bus because his mother hid his car keys to punish him for talking to a woman on the phone. Lisa informs everyone that Bart is acting very paranoid and asks that they act very nice to him, but everyone laughs at him instead. In the middle of the ride, Bart hears tapping on the window, but it is only Groundskeeper Willie, who says that he had to put down his mule and needs a ride. Bart's nightmare then comes true when a gremlin is attacking the bus. Bart keeps trying to warn everyone, but every time Bart looks, the gremlin hides and it even causes Otto to destroy Hans Moleman's AMC Gremlin. Meanwhile In their spaceship high above the Earth, the two aliens Kang and Kodos laugh at the "foolish human" who is very frightened of an imaginary monster, while an identical creature begins attacking their craft.
Skinner becomes annoyed and closes the window, then forces Bart to sit next to Üter, the German foreign exchange student. Bart eventually gets the emergency flares and throws one at the gremlin, knocking it off the bus, only to be picked up by Ned.
After arriving safely to the school, everyone notices severe damage done to the outside of the bus. Bart stopped the gremlin from destroying the bus, but with no one as an alibi, he is declared insane for his behavior and is put in a straight-jacket and also sent to the New Bedlam Insane Asylum for the rest of his life. On the way, Bart begins to relax at the thought of never having to worry about the gremlin, but at that very moment, the gremlin shows up at the ambulance's back window and shows Bart Ned's severed head, causing him to scream uncontrollably.
Meanwhile Back in the art gallery once again. Bart brings the viewers to the famous "Dogs Playing Poker" picture (Homer is frightened at this painting), explaining that they had a random story to go with it, but it was "far too intense and scary, " so instead, they had to put something about vampires together.
In a parody of Bram Stoker's Dracula, the family are watching TV to find out a vampire has been attacking people with him drained of his blood with two teethmarks on his throat where a black cape was found at the scene despite the obvious evidence. Later, Chief Wiggum assumes that it's the work of a mummy and orders the Egyptian wing of the Springfield museum to be destroyed. This convinces Lisa that vampires are real, though Homer debunks her, despite a report following of Mr. Burns buying the Springfield blood bank. Mr. Burns has blood visible from his mouth which he quickly slurps it up. The Simpsons are then invited to Mr. Burns' mansion for a midnight dinner in Pennsylvania. There it is obvious that Burns is a vampire (with Smithers acting as Renfield). No one believes Lisa, despite her obvious evidence (Burns' unknowingly mentioning over the entrance intercom how the family will be "fresh victims for his ever-growing army of the undead", Burns' shadow moving on its own etc.). Bart and Lisa find Mr. Burns' secret lair while cleaning themselves from spilling "punch" (really blood) on themselves, which can be easily accessed by staircase. The vampires in the lair awaken, causing the two to flee. Bart notices a "Super Fun Happy Slide" lever, and pulls it, turning the stairs into a slide.
Bart slides right into the clutches of a vampire woman while the rest of undead surround him. He's then presented to Mr. Burns who suddenly arrives transforming from a bat and stands over Bart menacingly before biting him in the neck. Lisa makes it back to her parents and warns them, but they don't believe her when Burns appears, blood on his very visible fangs, with a clearly bitten Bart, who drones in a zombie tone that nothing happened to him. Later that night at the Simpsons home, Bart, now a vampire, visits Lisa's window. Showing her that he's bitten and vamped some of the Springfield kids (Milhouse, Martin, Ralph and Jamie), with Lisa being next. He breaks through the window, pins her down and bears his fangs. Just as he's about to bite her, Homer, hearing the noise, bursts into the room stopping him. This quickly reveals to the family that he's a vampire while Bart changes into a bat and flees into the night. Lisa tells her parents that the only way to get Bart back to normal is to kill Mr. Burns. They return back into his castle and stake Mr Burns in his coffin (though not before Mr Burns briefly comes back to life and fires Homer).
The Simpsons are then eating dinner and Lisa finds out that her whole family is vampires, including Grandpa, who pretends to be the head vampire when in reality it's Marge. The family then swoops in on Lisa only to stop and wish everyone a happy Halloween while going through a Charlie Brown Christmas Special ending parody with Santa's Little Helper imitating Snoopy's dancing and Milhouse playing Schroeder's tiny piano as snowflakes fall from the kitchen ceiling.