In the middle of her psych class, Buffy daydreams about an uncharacteristically apologetic Parker, who begs her forgiveness after a surprise vampire attack. Professor Walsh's lecture snaps Buffy back to reality, and she looks down a few rows to see Parker putting his trademark moves on yet another female victim. After class, Xander finds Buffy and Willow and tells them of his recent employment as bartender at the campus pub.

That night, Buffy stops by the pub and sees Parker entertaining a girl at one of the booths. She bumps into Riley, who gives her the lowdown on Parker's womanizing habits. Buffy pulls up a stool at the bar, where Xander is finding some difficulty getting into the groove of the job. Fed up, Buffy is getting ready to leave when she is stopped by several guys who demand her presence at their table. Seeing Parker leave the pub with his latest prize, Buffy decides to accept the guys' offer. In no time, she finds herself guzzling several glasses of beer with her newfound friends. Meanwhile, at the Bronze, Willow notices Oz's overwhelming interest in the on stage band, Shy. He is particularly drawn to the lead singer, Veruca, a familiar girl who seems to share a mutual interest in Oz. Elsewhere, a man prepares a mixture of several chemicals and stores it in a keg of Black Frost beer, the same brand that Buffy was drinking with the guys earlier.

The next morning, Willow returns to the dorm and finds Buffy deeply fascinated by their television set. On their way out to psych class, Willow has to remind her roommate to get dressed. At class, Buffy eyes a classmate eating a sandwich. Buffy snatches the sandwich and hungrily scarfs it down. Later, Oz stops by Stevenson Hall and tells Willow that he's been invited by Veruca and her band to watch their show that night. Willow opts to take a pass, leaving Oz to go alone. While Oz heads to the Bronze, Willow decides to drop by the Grotto, where she finds Parker sitting by himself. She approaches Parker and proceeds to berate him for causing Buffy so much distress. In his defense, Parker tries to explain his philosophy of short-term relationships.

As Willow settles into the conversation, Buffy throws back another round of beers with the guys at the pub. Concerned with their increasingly primal behavior, Xander forces a reluctant Buffy to call it a night and head back to the dorm. Deciding that the other guys have had enough as well, Xander asks them to pay the bill. While he collects the money, one of the guys heads to the bathroom. Moments later, he emerges as a hairy, caveman-like grunt. While he knocks Xander to the floor, the others undergo similar transformations. Xander scares them off with his lighter, then runs into the back room to warn his boss, Jack. However, Jack reveals to Xander that he made the special formula in order to get back at the pretentious students.

Back at the Grotto, Parker attempts to lure Willow into seeing things his way. On the contrary, Willow doesn't buy his act for a second. Just as she's about to leave, the caveman storm into the grotto, dragging a couple of helpless girls inside with them. Before they can escape, Willow and Parker are knocked unconscious by the rampaging savages. Meanwhile, Xander gets Giles and takes him to Buffy's dorm, hoping the beer hasn't transformed the Slayer yet. Upon entering the room, they find Buffy drawing figures on the wall and pounding her chest, although her physical features are still unchanged. Xander and Giles try to secure Buffy, but she flees from the room.

Xander tracks Buffy down outside, but their attention is soon drawn to a pillar of smoke rising from the Grotto. Buffy makes it there first, and she finds the place going down in flames. Recognizing Willow on the other side of the flames, Buffy leaps to her friend's side. Buffy then spots a window wide enough for them to escape through, so she leaps up to kick it open. The cavemen take the escape route, followed by the two girls left behind. Xander helps Willow out through the window as Buffy pushes from inside. Instead of exiting right away, Buffy picks up a large piece of wood and inspects it thoroughly. Nearby, Parker regains consciousness and begs Buffy for help. Buffy swings the wood onto Parker's head, knocking him back to submission. She then drags him outside.

Soon, ambulances and fire trucks arrive on the scene to save what's left of the Grotto. Xander locks the cavemen in a van, knowing that the effects of the beer will wear off in several days. In a strange reenactment of her daydream from the other day, Buffy listens to Parker asking her to forgive him. Still under the influence of Jack's formula, Buffy responds by clobbering Parker with the wood once again.

~Episode Summary by: Alan Hufana