Shawn begins to feel the pressure of being in the middle of Cory and Topanga's ordeal. Their break-up is a touchy subject for him, as he wants to model his future relationships off theirs. When a classmate, Kenny, asks to borrow Topanga's pencil, Shawn flies off the handle, "They're not divorced, Kenny!"
Mr. Feeny, sensing he's losing control of the cl@ss separates Cory, Shawn and Topanga. Shawn argues, that Mr. Feeny is "contributing to the furtherance" of Cory and Topanga's "apartness". Feeny's had enough, however, and declares that the next outburst will put everyone in detention.
As if on cue, a creepy Janitor enters, empties the trash and leaves; sealing the detention fate of Cory, Shawn, Topanga, Angela and Kenny.
In detention, Feeny tells the group that they're being watched, and leaves the room. Shawn gets up to get a snack from his locker, only to discover the door is locked. The creepy janitor comes by and looks in. Shawn asks him to lock the door but he just smiles grimly and moves on.
Suddenly, the pull-down wall in front of the chalkboard snaps up, revealing a bloody message of doom: "NO ONE GETS OUT ALIVE!"
Cory suggests that Feeny may be trying to teach them a lesson. Shawn is comparing their situation to various horror films he's seen, when they hear a noise outside the room. Terrified that something horrible is coming for them, they're relieved when the door opens to reveal Eric and Jack.
They were playing basketball and decided to use the locker rooms. They comment on the eeriness of the empty school, and the group continues to suspect Feeny's involvement.
Kenny argues with Shawn briefly before the lights go out. When they come back on, Kenny has been stabbed in the head with a pencil. The group runs into the hallway in horror. The lights flicker and creepy music plays. They try to escape the school, but all the doors are chained and locked.
The lights flicker again and Feeny appears, but when Shawn touches him, he falls over. He's been stabbed in the back with scissors.
Back in the room, the group wonders what's going to happen next. Cory thinks the Janitor is the killer, and Shawn blames Topanga's breaking up with Cory for the horrible events.
Out in the hallway, the janitor is found dead in his trash cart. Eric offers to keep watch while the rest of the group go back in the cl@ssroom. While on "duty", he meets Jennifer Love Fefferman, whom he suspects as the killer. She denies it though, and he believes her, engaging her in a furious make-out session.
The pay phone rings and Eric picks it up. Apparently the killer wants them all to wait where they are, so he can come and kill them. Not liking the idea, the group runs to the library, where they split up. After "Feffy" kisses Cory comfortingly on the cheek, she is hit with a pile of books. Eric rushes to the scene, but before she can divulge information on the killer, more books are shoved off and Eric is buried.
Jack, is upset and realizes he can't live in his apartment without Eric's rental contribution. He goes to the window to jump in despair, but Angela talks him out of it. They are about to come back inside when a shrouded, skeleton-masked figure pushes them to their death. Only Shawn, Cory and Topanga are left. As the figure walks towards them, Cory demands, "Why are you doing this to us?" The killer takes Cory and Topanga's hands and clasps them together. Shawn rips off the killers mask to reveal another Shawn staring back at him.
The scene fades as Cory wakes Shawn from his detention slumber. "Feeny's looking at you like he's gonna kill you."
"No, he's not the killer. I am." Shawn tells Mr. Feeny to let everyone else go--he's the reason they're here. He goes on to explain the reason he interrupted class: Basically, if Cory and Topanga aren't together, he feels there's nothing he can depend on, and he's angry that there's nothing he can do to fix it. After Cory, Topanga and Mr. Feeny assure Shawn that it's not his fault, Mr. Feeny lets them all go.