In a parody of the original Frankenstein film, Marge warns viewers that the following program (The Simpsons) may give their children nightmares, so she suggests the adults to "tuck your children into bed tonight instead of writing us angry letters tomorrow." The show then begins.

When Homer comes back from trick-or-treating, he notices Bart and Lisa are telling ghost stories (while Maggie watches) in Bart's treehouse. He climbs up and eavesdrops while Bart comments on Lisa's first story. Bart begins telling his own story.

In a parody of the 1950 story by Damon Knight from Galaxy Science Fiction (and its 1962 Twilight Zone episode adaptation) titled To Serve Man, the Simpsons are having a barbecue in their backyard until an alien spaceship suddenly abducts them. When they arrive on the ship, they meet Kang, Kodos, and Serak the Preparer, who treat the Simpsons extremely well by giving them countless amounts of food to hold them over, until the great feast at Rigel 4. These three aliens call themselves Rigellians.

After the family is weighed on a giant scale and the Rigellians constantly make references to food, Lisa becomes suspicious and thus thinks to herself about the aliens' true motives. One night, she wanders around the spaceship and heads into the aliens' kitchen, when the chef Serak cooks something to "give the humans the perfect flavor".

After he leaves the room, Lisa grabs the book called "How to Cook Humans", runs to her family and accuses the Rigellians of feeding them all up to eat the humans. However, it is then revealed that Lisa did not see the whole title of the book, which is actually called "How to Cook for Forty Humans". The Rigellians feel sad, disappointed, and angry at the family, so they send the family back home to live the life of "not gods, but normal human beings". Then, Lisa speculates that they, the Simpson family, may be the true monsters after all while the family blames Lisa for her actions.

Lisa reads a classic tale of terror, "The Raven", penned by Edgar Allan Poe Homer, a wealthy, yet distraught lover lamenting the loss of his Lenore, sits, asleep, with a book titled "Forgotten Lore Vol.~II" on his lap. He's soon disturbed from his slumber and awoken by a repeating tapping on his chamber door. Homer's spooked by a rustle heard outside. Screaming, Homer hides behind his reading chair and utters, "Sir, or Madam, truly your forgiveness I implore; But the fact is I was napping, and so gently you came rapping, And so faintly you came tapping, tapping at my chamber door, That I scarce was sure I heard you." Homer proceeds to approach the chamber door and throws it open while covering his eyes. There's nothing there but darkness.

Suddenly, there comes a tapping on the window. Homer opens the window, and a raven flies into the room and perches above the chamber door upon a bust of Pallas. Homer attempts to communicate with the raven, but the bird only replies with, "Nevermore." The bird continues with this reply and begins to anger Homer. Homer lunges for the Raven, who flits away. Homer chases the bird across and around the room, but it remains barely out of reach. Homer and the raven's chase makes a mess of his chamber and results in Homer throwing a potted plant at the Raven, who dodges the projectile. The plant pot hits Homer on the head, and tiny ravens dance around his head, chanting, ``Nevermore, Nevermore, Nevermore...

The chase continues. The Raven plucks books from the shelf and drops them, before returning to its place atop the bust of Pallas. Meanwhile, below, the carnage it wrought upon the room, Homer seemingly descended into madness. The narrator concludes, "And the Raven, never flitting, still is sitting, still is sitting on the pallid bust of Pallas just above my chamber door; And his eyes have all the seeming of a demon's that is dreaming, And the lamp-light o'er him streaming throws his shadow on the floor; And my soul from out that shadow that lies floating on the floor shall be lifted - nevermore!"

Bart and Lisa talk about the tales before going to bed and Bart didn't find the story that scary, not knowing Homer was freaked out by all of them. Everybody goes to bed, but Homer has trouble sleeping that night and decides he hates Halloween after hearing the Raven outside.