Seth and Evan are two high school seniors who have been best friends since childhood. The two are about to go off to different colleges. After Seth is paired with Jules during home economics class, she invites him to a party at her house that night. Their friend Fogell reveals his plans to obtain a fake ID, so Seth promises to buy alcohol for Jules’ party with money she gives him. Evan runs into his crush Becca and he offers to get her some vodka for the party. Despite Fogell’s fake ID having only one name, “McLovin,” Fogell successfully buys the vodka, but is knocked out at the last second by a robber. When police officers Slater and Michaels arrive, Seth and Evan believe that Fogell is being arrested. In reality, the officers agree to give Fogell a ride to the party.
Outside, Seth is hit by a car. In exchange for Seth and Evan not telling the police, the driver promises to take them to another party where they can get alcohol. Meanwhile, Slater and Michaels take Fogell on a ride-along and then bond with him. Despite being on duty, they start drinking, using their sirens improperly, and shoot their firearms at a stop sign. At the party, Seth fills detergent bottles from the basement with alcohol he finds in the fridge and dances with a drunk woman, who stains his leg with menstrual blood, while Evan is made to sing by some men high on cocaine. About to leave, Seth is confronted by the host for dancing with his fiancée. A brawl ensues. The fiancée calls the police, while Seth and Evan escape.
Evan and Seth argue, and Seth is once again hit by a car – the police cruiser driven by Slater and Michaels. They plan to arrest Seth and Evan, but when Fogell comes out of the car, Evan makes a run for it, while Seth and Fogell escape with the alcohol. Eventually all three make their way to Jules’ party. At the party, Seth’s stories of the night make him popular. Becca wants to have sex with Evan, but he respects her too much to go through with it while she is drunk. Meanwhile, Fogell impresses Nicola and goes upstairs to have sex with her. Seth drunkenly attempts to kiss Jules, but she turns him down because she neither drinks nor wants Seth while he is drunk. Seth believes he has ruined any chance of a relationship with Jules, and passes out, accidentally headbutting her, leaving her with a black eye.
Slater and Michaels bust the party. Seth wakes up and escapes, carrying an intoxicated Evan. Slater interrupts Fogell and Nicola, who runs off. Slater is angry at Fogell for ditching them, but Michaels points out they have just “cock-blocked” him, and they apologize, reconcile, and reveal they knew all along that Fogell was not 25. They played along, wanting to show cops can have fun. To make it up to him, they pretend to arrest Fogell to make him look “bad-ass.” They resume their bonding, eventually destroying their car with a Molotov cocktail while Fogell shoots it with Slater’s firearm.
The next morning, Seth and Evan go to the mall and run into Jules and Becca, and the men pair off with the women. Seth takes Jules to buy concealer for her bruise, while Evan and Becca leave to buy a new comforter to replace the one that Becca ruined from being sick.