Cory is bumming everybody out, and that's why he's not invited to Kimberly Sussman's party. Even Shawn admits that he's getting tired of "Cory the Mope."
Despite his lack of invitation, Cory shows up at the party. He manages to flirt his way in, and once inside he becomes the life of the party--telling jokes and dancing. Everyone wants to know what happened to the old "downer" Cory.
Shawn discovers Cory in the bathroom with a pint of Whiskey. After some coercion, Shawn partakes as well. The two get drunk and stumble down the street, enjoying each others company and talking about how they peed on a police car.
They convince a bum to buy them some beer, but as they crack the first can, a police car (the same one they peed on) pulls up and arrests them.
In Cory's kitchen, the boy's are lectured by Alan, who accuses Shawn of initiating the ordeal. When Amy takes Alan in the other room for a separate discussion, Shawn tells Cory that he'll take the heat, because people expect it from him. "Your parents have you on this pedestal, and I'm not gonna let you fall off."
When Cory's parents return, with the verdict that the friends need some time apart, Cory tells the truth: He did it because he was depressed about Topanga, and he made Shawn drink because he didn't want to be alone. Alan apologizes to Shawn, and the boys agree to never drink again.
In Mr. Feeny's cl@ss, Shawn interrupts with an outburst about being bored with "Feudalism". He goes to far, even for Shawn, and Feeny kicks him out. Cory follows him and they walk to Shawn's apartment, where Shawn takes a beer out of the fridge.
Cory objects, but Shawn explains, "If you're worried about me, you stop worrying about Topanga." Jack enters and is upset to see Shawn with a beer. Chet used to be an abusive drunk, so he's worried about Shawn. "Alcoholism is in our family, and you shouldn't drink!"
Angela and Topanga arrive. Topanga is upset to learn of Cory's drunkeness at the party, but she's more concerned about Shawn. Angela tries to take Shawn away to talk in private, but Shawn gets mad and pushes her into the door. She leaves, crying, and Shawn realizes the seriousness of the situation.
The next day, Shawn visits Cory's house to apologize to Alan and to tell him he doesn't have to worry about him drinking anymore. Alan forgives him, but Cory's still grounded for a month.
At school, Shawn also apologizes to Mr. Feeny for his outburst, and explains that he and Jack are seeing a counselor. He apologizes to Topanga and Angela, and all is well.