It is Halloween, and to celebrate, Miss Simian is hosting a Halloween-themed show and tell for her students. The event seems rather dull until Gumball's turn; for his presentation, he tells his class a Halloween story about Gargaroth. The story tells of Gargaroth, a hideous monster who initially demanded a princess's hand in marriage. The king agreed to this, but the princess was so disgusted by Gargaroth's appearance that she left him at the altar; saddened, Gargaroth began eating everyone around him until he was banished to the underworld and all mentions of his name were forbidden, for any mentions of the name would allow him to re-enter the mortal realm.
As Gumball tells the story, he repeatedly mentions the name "Gargaroth", which terrifies his classmates. While somewhat impressed, Miss Simian still finds the story rather lackluster; that is until Sarah's head begins to levitate and all sorts of paranormal activities occur. Panic ensues in the classroom and everyone in the room (except Gumball and Darwin) flees in terror. Once everyone has left, it is revealed that Carrie is the one behind the big scare; this big scare was all part of Gumball's and Carrie's plan: to have the school under the false belief that Gargaroth (performed by Carrie) is possessing it, and that the ghost exterminators (Gumball and Darwin) can get rid of him for the price of Halloween candy.
Gumball and Carrie are ready to put their plan to action, but Darwin has other plans, for he believes that the scam his older brother and Carrie are trying to pull is terribly immoral, and he refuses to take part in it. Darwin's opinion on the scam quickly changes once Gumball mentions that this is Darwin's opportunity to get close to Carrie (whom he has a crush on).
After Darwin's brief romantic fantasy of him and Carrie together, the Watterson brothers begin to put the plan to work. Masquerading as ghost exterminators, Gumball and Darwin begin convincing several of the students and staff that Gargaroth is haunting them, with Carrie causing unearthly activities to support their claims. The trio is successful in both scamming the school and eventually, the entire town out of candy. As they leave, however, the school floor begins to crack and the sky starts to glow a dark red.
Once they finish with their scam, the three return to the Wattersons' house; Gumball, Darwin and Carrie are about to eat the candy they "earned" in the attic. Carrie, lacking a body to do so herself, asks Darwin very sheepishly whether she can temporarily possess his body to consume their goods. Their moment is cut short, as Gumball looks out the window and notices the ominous aura surrounding Elmore Junior High. The three decide to investigate what is occurring at the place.
As they arrive at the scene, Mr. Small tells them that Gargaroth has taken over the school; the trio is shocked to hear that their originally fictitious story is actually truthful, but the three put aside their concerns to deal with the problem at hand.
Very slowly, the three enter the school building; Gargaroth rises from the underworld and prepares to attacks the children. They make few attempts to fight him, all of which fail. Shortly after Darwin states they deserve Gargaroth's attacks for the actions they have committed, Carrie realizes that the only way to get rid of him is to satisfy his hunger. If Gargaroth consumes all of the sweets, he will explode. Both of the Watterson brothers (although Gumball more reluctantly) agree to feed him their candy, so Carrie casts a spell that transports the candy from the attic to Gargaroth's mouth. When it seems as if Gargaroth only requires one last piece of candy, Gumball decides to take the last lollipop for himself.
Out of options, Carrie realizes that she must selflessly become Gargaroth's bride and live in the underworld forever, much to Darwin's horror. As Gargaroth is about to kiss Carrie and seal the marriage, Gumball grudgingly feeds him the last candy he has, causing Gargaroth to explode and the school to return to its normal state. Once the children exit the building, they are hailed as heroes for their efforts.
While the crowd carries Gumball away, Darwin tries to ask Carrie out on a date, but he is too shy to do so properly. However, Carrie is willing to spend some time with him and asks if he would like to get an ice cream with her; before she can receive her answer, though, Gumball pulls his brother away, ending the episode.
[The episode opens with a song as the hallway of Elmore Junior High are shown, decorated with all kinds of Halloween props.]
Idaho: [Sung; in a deep voice]Double, double toil and trouble
Fire burn, and cauldron bubble
Eye of newt and toe of frog
Wool of bat and tongue of dog.
[In Miss Simian's class, all the students are wearing Halloween costumes.]
Idaho: Thank you! [goes back to his seat]
Lucy Simian: [sighs] Next.
[Tobias walks to the front of the class. His face is purple and swollen up.]
Lucy Simian: Wow! Good Halloween mask.
Tobias: It's not a mask, I'm allergic to the face paint.
Lucy Simian: [grunts] C minus then, go to the infirmary.
[Tobias faints on the way out.]
Lucy Simian: Next!
[Gumball sits up in front of the class.]
Gumball: For my show and tell, I have a Halloween story.
[The sky darkens outside; ominous music plays.]
Gumball: Legend tells of a terrible monster that dwells in the Underworld, so evil and ugly that words cannot describe it. So I'll use mime.
[Gumball turns into an ugly, deformed version of himself for a moment, then turns back.]
Gumball: Anyway. Every year, the king of the Underworld sacrificed a soul for the creature to devour, until one year he demanded the hand of the king's daughter in marriage. The king agreed, on the promise of no further sacrifice. But the princess, disgusted by the monster's appearance, left him at the altar. In his sorrow, the monster ate everything at the banquet table and every soul around it.
[Everyone in the class seems disturbed by the story.]
Gumball: He was banished, and all mentions of his name forbade, for just speaking his name would be to invite him into our world. Which is why you should never utter the words: Gargaroth the Devourer.
[The students gasp, holding their face in shock, except Tina. They continue to gasp everytime he mentions the monster's name.]
Gumball: That's right, "Gargaroth" is a name you should never say. The mere mention of Gargaroth would summon Gargaroth into our world. And believe me, Gargaroth is not a nice guy. Gargaroth—
Carmen: Can you please stop saying it?!
Gumball: [gasps] Did I say "Gargaroth?"
[Lightning strikes outside, causing the kids to scream.]
Lucy Simian: [shrugs] Yeah, that wasn't scary. I'll give it a— AAAAAIE!
Gumball: An A? Really?
Lucy Simian: No, I meant: AAAH!
[Miss Simian points to Sarah, whose head suddenly started levitating. The pupils scream as a series of paranormal events unfold, with Bobert's calculator spelling "BOO" upside down, slamming doors, and all objects in the room floating up. Everyone flees, except Gumball and Darwin.]
Gumball: End scene.
[All the chairs and desks drop, perfectly stacked up. Carrie appears in the middle of the classroom, laughing, and then teleports next to Gumball as Darwin frowns in their direction.]
Gumball: [laughs] Good job, Carrie! This is gonna work.
[They laugh maniacally.]
Gumball: Okay, I saw Principal Brown buying candy for the school store.
Carrie: Then let's hit him first.
[Carrie disappears. Darwin walks up to Gumball with a disapproving look on his face.]
Gumball: Okay yeah, I'm gonna need more screaming and less judgmental staring in your performance.
Darwin: It's not a performance.
Gumball: Alright, method acting. I respect that.
Darwin: No! I really am judgmental, 'cause what we're doing is wrong!
Gumball: Eh, which part? The part where we pretend to summon Gargaroth and use Carrie's powers to scare people, the part where we pose as paranormal specialists to get rid of him, or the part where we get paid with everyone's trick-or-treat candy?
Darwin: Every part! What is wrong with you?!
[Gumball stares through the window, tears welling up in his eyes.]
Gumball: I'm tired, Darwin. I'm tired of having to wear a mask on Halloween, because people wouldn't give me candy if they knew if it was me. Because of my reputation, Darwin. [Darwin glares at him] My reputation. [turns to Darwin] Alright, fine, it's because I'm greedy. But don't worry, there'll be plenty for you too!
Darwin: [crossing his arms] Nothing can make me go along with this dishonest scam.
[Gumball slithers around Darwin just like a snake.]
Gumball: Not even to get close to Carrie? If she's gonna eat all that candy, she'll need a body to possess.
[Darwin blushes and sings a song while he pictures himself dancing with Carrie.]
Darwin: Okay, when do we start?
[Gumball knocks on the door to the principal's office. He scans Principal Brown's body with a flashlight taped to a calculator, and enters the office along with Darwin.]
Nigel Brown: What are you doing here?
[Darwin goes through different folders in the desk, throwing papers everywhere.]
Gumball: [licks a pen] Hm. Traces of ectoplasmic residue.
Darwin: Telekinetic activity.
Nigel Brown: Can you please explain to me what's going on?
Gumball: We're here to get rid of Gargaroth the Devourer. For a small fee, of course.
[Gumball and Darwin are kicked out of the office. Principal Brown slams the door, but opens it again shortly after. All his papers and furniture are moving in a tornado across the room.]
Nigel Brown: How much?
Gumball: We'll take those two bags of candy in the corner over there.
[Principal Brown hands them the candy as "How Low Would You Go?" begins to play. Gumball and Darwin walk through the corridor and try to high-five Carrie, but their hands go through and they hit each other's faces instead. Carrie possesses Coach's body, forcing her to go on a rampage through the cafeteria. She climbs up the wall and onto the ceiling, causing everyone to run in panic.]
Bean: [points to Coach] It's Gargaroth!
[Coach falls off the ceiling, breaking the table underneath. Gumball and Darwin barge in, armed with vacuum cleaners.]
Gumball: Fire 'em up.
[Gumball and Darwin start their vacuums, sucking in all the food and objects in Coach's body, as well as Carrie.]
Gumball: She wasn't even possessed when she ate this!
Carrie: I'm getting paid double for this one.
[At the swimming pool, Tobias jumps, only to hit the bottom of the pool as all of the water is being held up by an invisible force.]
Rocky: [gasps] Gargaroth!
[Gumball and Darwin burst into the room, still holding vacuums.]
Darwin: We'll take it from here.
Gumball: For a small fee.
Tobias: Thank goodness you're here!
[Gumball and Darwin start the vacuums and all of the water drops in the pool, leaving Tobias to float. Rocky and Tobias then hand all of their candy to them. The song is interrupted for a moment when Darwin trips on the cable of his vacuum, but he manages to plug it somewhere else. Meanwhile, Mr. Small meditates in his office and starts levitating.]
Mister Small: [gasps] I finally reached a state of pure enlightenment!
[He looks up, only to see he is actually being sucked up by the ceiling fan.]
Mister Small: No no no no! Stop, STOP! HELP! [screams]
[Gumball and Darwin turn their vacuums on, successfully stopping the fan. Mr. Small rewards them with raisins.]
Gumball: Hey! Raisins?
Gumball & Darwin: [shaking their heads] Hm-hm-hm.
[They walk away as the fan starts again, pulling Mr. Small back into his office.]
Mister Small: Gargaroooth!
[Mr. Small's scream echoes through the corridors, while Gumball, Darwin and Carrie walk towards the exit.]
Darwin: I'm glad we're gonna quit while we're ahead for once.
Darwin: We are quitting, aren't we?
Darwin: You're lying, aren't you?
Darwin: We're gonna scam every bit of candy in this town, aren't we?
[When they leave the school, the screen begins to shake and red light shines through cracks forming in the ground. Outside, the sky has turned red, and people are running away screaming as cars and chunks of the road start levitating.]
[In the Wattersons' attic, Gumball, Darwin and Carrie stand on top of a giant pile of candy which fills up the entire room.]
Gumball: Ah, there. Every last bit of candy in Elmore! Alright, dig in!
Carrie: [blushes] S-so, Darwin. Do you mind if I borrow your body to, y-you know?
Darwin: [giggles] No problem.
[Darwin sprays breath freshener in his mouth, but accidentally sprays Gumball's eyes instead, causing him to fall over.]
Gumball: Ow! [stands up facing the window] Uh, guys, did the weatherman say "cloudy with a chance of apocalypse?"
[The three of them look out the window and notice the red light ray above Elmore Junior High. They hurry to school, where a crowd has gathered.]
Darwin: What's going on?
[A deep growl is heard coming from the building.]
Mister Small: Gargaroth has taken over the school!
Darwin: What? He's real?!
Carrie: I didn't know. I thought he was just a ghost ghost story!
Nigel Brown: The Wattersons, thank goodness! They'll save us from Gargaroth the Devourer.
[The crowd cheers.]
[Gumball, Darwin and Carrie walk carefully through the school's hallway.]
Gumball: I always knew I'd get my fifteen minutes of fame, I just didn't think they'd be my last. [gulps] So Carrie, in the story, how exactly do they manage to banish Gargaroth? That part was light on detail.
Carrie: Through the sacrifice of a lone, selfless hero.
Gumball: Yeah, uh... Still pretty vague, to be honest.
[They come across Gargaroth, who starts rising from a hole in the ground.]
Gumball: Wait. If your story's true, all it takes is a hero. This hero.
[Gumball attempts to suck Gargaroth into his vacuum multiple times, but nothing happens.]
Gumball: ...Right, maybe not.
[The monster growls menacingly and starts going after them.]
Darwin: We deserved this, we shouldn't have scammed all that candy!
Carrie: Yes, we need to feed him the candy!
Gumball: No way, I worked way too hard for that!
[Gargaroth's many arms extend and eventually grab Gumball, Darwin and Carrie, dragging them to him.]
Carrie: You need to make a sacrifice, like the hero in the story!
[Gargaroth prepares to eat them.]
Gumball: [shudders] Okay!
Carrie: Gargaroth! If Your Grossness agrees to release us, we will give you what your heart desires. A sacrifice to your infinite fleshitude.
[Gargaroth burps and puts them down.]
Carrie: Maximus Haribo!
[Carrie's spell opens a hole in the ceiling, transferring all of the candy in the Wattersons' attic directly into the monster's mouth.]
Gumball: He's a monster!
Darwin: Uh, duh?
Gumball: That's not what I meant. He's not even taking off the wrappers!
Carrie: Look out. One more mouthful and he'll blow!
[The kids take cover as it seems Gargaroth is about to explode, but he only lets out a burp instead.]
Carrie: Quick! Is there any more candy left?
[Gumball picks up a lollipop and hides it behind his back.]
Carrie: Then run again.
[They start running again with Gargaroth's arms reaching out for them.]
Gumball: Remind me to never believe any more of your stories.
Carrie: That's it! He's only here because we made people believe in him!
Gumball: [gasps] Then maybe, if we close our eyes and stop believing...
[Gumball places his hands in front of his eyes and concentrates, but he ends up running into a wall at the end of the corridor.]
Darwin: [gasps] Gumball!
Darwin: Gargaroth. Stop! Why are you doing this? Is it really food you seek? Perhaps the emptiness isn't in your stomach, but in your heart.
[The monster seems calm for a moment, but quickly returns to his violent ways and grabs Gumball and Darwin. Carrie appears in front of him.]
Carrie: Gargaroth, no! If you promise not to destroy this world, I will fill the void in your heart.
Darwin: W-what are you doing?
Carrie: It's the only way. Gargaroth, I will be your bride.
[Carrie and Gargaroth have a wedding ceremony in the library. Gargaroth's speech seems to be composed of only belching and farting sounds.]
Carrie: I do. And you, Gargaroth the Devourer, do you promise to share your clogged heart in health, but mostly sickness, and join me for eternally horrible matrimony in the Underworld?
[Gargaroth lets out another crude noise.]
Carrie: I'll take that as a yes. Then with this kiss, let us seal our unholy union.
Darwin: [tears up] Why did she have to be sacrificed?
[The newlyweds prepare to kiss.]
Darwin: There has to be another way!
[Gumball pulls out the lollipop behind his back.]
Darwin: Noo... [sobs]
Gumball: Ugh! Alright.
[Gumball throws the last piece of candy into Gargaroth's mouth, causing him to explode and cover the trio in green slime.]
Free at last
[With the school finally free from Gargaroth's influence, the crowd hails outside.]
Gumball: Yeah, yeah, whatever.
[Gumball wipes some slime off his face and reluctantly lets the crowd launch him up.]
Darwin: Okay, well, bye!
Darwin: Oh, oh! U-unless you're hungry?
Carrie: Not really. What was left of that candy looked pretty well digested.
Darwin: Oh, right. Nevermind...
Carrie: O-or, we could just get an ice cream?
Darwin: Uh! I-I'd like—
Gumball: Come on already!
[Gumball drags Darwin by the hand, ending the episode.]