It is the day before Halloween and Buffy, Willow, Oz and Xander are in Xander's basement carving pumpkins ready for the big night. Xander is organising a stay at home horror video night (they stay in after the problems with Ethan and his magic costumes), unfortunately, the video shop have given him the wrong video and instead of Phantasm they've given him Fantasia. Oz mentions the Frat Halloween party that they've been invited to and Willow invites Xander along. Buffy isn't really joining in, she's still moping over Parker. She decides to bail and after she's gone Xander takes a vote on how many people want to hit Parker (it's unaminous)

As Buffy is walking through Sunnydale a boy in a demon mask jumps out in front of her and she punches him before she realises what she's doing. he's not happy about it.

The next day, Buffy and Willow are walking through the Uni corridors discussing magic. Willow feels that she is plateauing and Buffy warns her against trying spells beyond her experience. When Oz joins them he also warns Willow not to mess. As they are walking, Buffy spots parker and turns around in the other direction so not to meet him. Willow tells her to get over him and look forward to the party that night.

Buffy thinks that Giles will want her patrolling and goes over to see him. She is a little shocked when Giles opens the door and is dressed as a Mexican in sombrero and poncho. Giles defends himself, saying that he's getting into the Halloween spirit, before reminding Buffy that Demons and Vampire's find Halloween vert crass and stay at home. he tels her not to go patrolling and go to the party instead.

Anya goes around to Xander's she wants to know what is going on with their relationship. Xander conceeds that there are date like qualities at work here and invites her along to the Frat party as his date. He tells her to wear a scarey costume.

Buffy goes back to Uni to get the assignments she missed of Prof. Walsh. Walsh is very abrupt with her student and warns her that if she misses any more lectures she's off the course. Riley gives Buffy her assignments and apologises for Walsh and tells her to have fun on Halloween.

At the Frat house, the boys are getting the finishing touches ready for the party. Oz lends them his sound system (Mi Casio es su Casio) and Xander learns some women-wooing techniques frat-style. One of the Frat boys has found an old book and is drawing a symbol out of it on the floor of the main party room. Oz accidentally cuts his thumb and a few drops of his blood falls on the symbol. No one notices it start to ripple. Or the fake spider near it turning into a real one.

Joyce is finishing off Buffy's Halloween costume, recycled from 12 year old Buffy's Little red riding Hood costume. Joyce gets all nostalgic for the good old days and Buffy still blames herself for the divorce. Joyce tries to convince her that it's not her fault and that she has loads of friends that love her.

Buffy in her Red Riding Hood costume meets up with the others outside the frat house. Xander is going for the cool secret agent look (James Bond), Buffy reckons that if they do become their costumes Xander would more likey be cool head-waiter-guy. Xander asks her what's in the basket, to which she replies weapons. Willow is is dressed as Joan of Arc. She says she fells close to her (nearly beeing burned at the stake) and that Joan had a close relationship with God. Xander and Buffy look confused until Oz moves his shirt to reveal a name tag saying "God" on it. Xander is jealous of the clever idea.

Inside, at the party on of the Frat guys is getting his date to put her hands in bowls of slimy grapes, saying they are eyeballs. When she takes her blindfold off they have changed into real eyeballs. Everything at the party goes crazy, with people runing around in panic trying to escape and getting injured in the stampede.

The Slayerettes have let themselves in and are working their way through the maze to the party. Willow scares herself when she walks into some cobwebs and Xander shows off his girlie scream when a skeleton pops out of a cupboard, much to the others amusement. Things take a turn for the weird when a huge spide crawls all over Willow, they find a puddle of real blood on the floor and they are attacked by a flock of bats. One of the bats transforms back into rubber after the attack.

Anya arrives at the party in her scary costume (a rabbit) but she can't get in because the front door has vanished. She walks back to the front of the house in time to see a girl banging on an upstairs window in terror before the window is enclosed by stone.

Inside the house the gang are trying to get out but the doors are gone. They find Chaz (the one who drew the symbol) hiding in a closest, hysterical with fear, saying it's alive. They don't notice the Skeleton come up behind Buffy and stab her in the back. Buffy whirls around and smashes it. it hits the floor and becomes plastic again. When they turn back the closet is gone.

Buffy takes charge, but Willow argues with her. She wants to use her magic and Buffy won't let her.

Anya gets to Giles's (still wearing his Mexican outfit) and tells him that Xander (and the others) are in danger and they have to save them.

Back in the house Buffy and Willow are still arguing. Xander tries t obreak it up but both girls ignore him. Willow storms off, Oz following, to find her own way out. Xander tries to calm Buffy down but she ignores him, it takes a few moments for him to realise that he is invisible and the others can't see or hear him. Willow finds some stairs that go up to the next floor. As they are exploring Oz starts to change into a wolf and when Willow goes to help him he scratches her before running off.

Xander, wandering alone, finds a mirrir and is relived to find that he still has a reflection. The fake-head on the table behind Xander tells him that it can see him too. Xander runs off.

Oz is sitting in a bath, half changed, repeating mantra-like that he will not change. Willow in another room chants the guiding spell and is pleased that it works, but it goes wrong and spirals out of control.

Buffy, somewhere else in the house can hear Willow's screams and runs to find her. She runs through a door that opens onto a sheer drop into the cellar. She lies there dazed until dead hands start thrusting out of the ground grabbing her. She manages to crawl away and out of a hole which leads into the third floor party room.

Giles (no longer dressed up) and Anya (still in costume) have got the the Frat house, where they is still no front door. Giles decides to make a door and pulls out a chainsaw and cuts his way in.

All four of them have managed to find their way into the party room, relatively unscathed, Oz is no longer wolfy, Willow managed to escape her spell and the others can see and hear Xander. they realise that something is feeding off their fears and Xander locats the book Chaz used to write the symbol on the ground. It's in Celtic, but Willow slowly translates it. the symbol is the Mark of Gachnar a demon that feeds off people's fears in order to manisfest itself.

Giles comes crashing in with his chainsaw, with Anya close behind and Giles translates some more of the book. Buffy punches a hole in the symbol before Giles can tell her that doing so with call Gachnar forth.

The ground underneath the hole begins to glow bright white as Gachnar appears. He is fearsome looking but only 6 inches tall. Xander taunts it and Buffy destroys it by standing on it.

They head back to Giles's appartment and set to work on eating all the chocolate he bought for the trick or treaters. Willow eats a little too much. Giles is reading the rest of the book and realises his mistake. he shows Buffy the picture of Gachnar again and points to the writing underneath which translates from Gaelic as 'Actual Size'. Buffy shrugs and shuts the book.