The story opens with Linus and Lucy going out into a nearby pumpkin patch to find a pumpkin to use as a jack-o'-lantern. After rejecting a couple of smaller choices by Linus, Lucy points to the biggest pumpkin in the patch, which Linus clumsily rolls back home. When they get home, Lucy takes a big knife and slices into the pumpkin to gut it, at which point a horrified Linus says, "Ohhhh, you didn't tell me you were going to kill it!", and starts crying.
This is followed by an opening sequence, in which trick-or-treaters (dressed as Mr. Hyde, a witch, and three ghosts; most likely the children in the special) get pursued by sinister-looking phantoms representing Halloween. The trick-or-treaters are forced to hide in a near-by pumpkin patch until the coast is clear, at which point the title is shown on screen along with Charles M. Schulz's creator credit, followed by an owl hooting as it flies off a tree branch and towards the audience.
With autumn already in full swing, Charlie Brown is busy raking leaves with Snoopy's help. Linus sees the pile and jumps right in the middle of it, forgetting he had a wet lollipop (called a sucker in this special) in his possession. Moments later Lucy comes with a football for Charlie Brown to kick. He initially refuses but Lucy shows him a contract, which she says promises she will not pull the ball away, but when Charlie Brown is about to kick the ball, she does pull it away, which sends him landing flat on his back, like always.
LinusWritesToPumpkin
Linus writes a letter to the Great Pumpkin.
Later, Linus writes a letter to The Great Pumpkin, to Charlie Brown's disbelief, Snoopy's laughter, Patty's assurance that the Great Pumpkin is a fake, and even to Lucy's violent threat to make Linus stop ("You better cut it out right now or I'll pound you!"). Linus laments in the letter that "more people believe in Santa Claus than in you (The Great Pumpkin), but let's face it; Santa Claus has had more publicity. But being number two, perhaps you try harder" (a tongue-in-cheek jab at Avis Rent-A-Car's popular slogan of the day).
After Linus mails his letter to the Great Pumpkin (using his blanket to open the mailbox after Lucy refuses to help), Charlie Brown dances when he receives an invitation to go to Violet's Halloween party. His bubble is quickly burst by Lucy who mentions there were two lists, people to invite and people not to invite; Lucy is certain Charlie Brown's name was on the wrong list.
On Halloween night, the gang gets their costumes ready. Lucy dresses as a witch, while the other kids dress up as ghosts. "Pig-Pen" is easily recognized by his trademark cloud of dust, while Charlie Brown has eyeholes cut out all over his sheet, matter-of-factly stating he had a little trouble with the scissors. Sally asks asks if she can join the gang trick-or-treating. Lucy explains how to trick-or-treat and Sally asks if it is legal.
Before going trick-or-treating, the gang stops off at the pumpkin patch to make fun of Linus's missing out on all the fun as last year (especially when he asks if they came to sing "pumpkin carols"). Linus remains convinced that the Great Pumpkin will indeed come because he thinks the patch he is in is sincere enough and even convinces Sally to stick around and wait with him. The rest of the gang go off leaving Sally and Linus behind.
During trick-or-treating, everyone else gets assorted candy, gum, apples, cookies, popcorn balls, and even money. However, at every house, Charlie Brown gets the same thing — a rock. After tricks-or-treats, and another quick stop at the pumpkin patch to rib Linus and Sally again, the gang all go off to Violet's Halloween party.
Meanwhile, Snoopy, wearing his World War I Flying Ace gear, climbs aboard his Sopwith Camel (in reality, his doghouse) to do battle with the Red Baron. After being shot down, Snoopy makes his way across the countryside, before briefly crashing the Halloween party.
The-great-pumpkin
Linus mistakes Snoopy for the Great Pumpkin.
He then makes his way to the pumpkin patch where Linus and Sally are still waiting for the Great Pumpkin to show up. Linus hears Snoopy's rustling, and believes it is the Great Pumpkin. When Snoopy (still hidden in the shadows) rises above the pumpkins, Linus promptly faints. When Sally sees it is only Snoopy, she becomes outraged over missing tricks-or-treats and the Halloween party, and threatens to "sue" Linus. She storms out of the pumpkin patch with the other children, leaving Linus by himself, still convinced the Great Pumpkin will come. When promising to put in a good word for them, he accidentally says "If the Great Pumpkin comes", instead of When. After he realizes his mistake, he declares that he is doomed and that "one little slip like that can cause the Great Pumpkin to pass you by." The camera then zooms out to reveal the entire pumpkin patch as he calls out, "OH GREAT PUMPKIN, WHERE ARE YOU?!"
LucyTakesOffLinusShoes
Lucy takes off Linus' shoes before he passes out.
When 4:00 a.m. rolls around on November 1, Lucy gets up to check on Linus. Seeing his bed empty, she goes out to the pumpkin patch to find him lying on the ground shivering, covered in his security blanket. Lucy grudgingly walks him home and to his room, taking off his shoes and socks. He passes out in his own bed as Lucy puts the covers on him before angrily walking out of his room.
Later on that day, Linus and Charlie Brown are at the wall talking about the previous night's events. When Charlie Brown tries to console Linus saying "I've done a lot of stupid things in my life, too", Linus blows a fuse and angrily vows to Charlie Brown that the Great Pumpkin will come next year, his ranting continuing as the end credits roll.