The students of Sunnydale High school are spending the afternoon at the zoo. Besides the standard zoo animals, this facility has a special new hyena exhibit, marked "Positively No Admittance." This piques the interest of Sunnydale's obnoxious cool crowd, who have already had their fun tormenting Buffy and a shy, bookish student named Lance. After grabbing poor Lance's notebook, they enter the forbidden hyena house, forcing him to follow. Xander, worried about his timid classmate, decides to come to his rescue. As they wait for Xander, Buffy and Willow meet an eccentric zookeeper, who claims the hyenas can understand human speech -- they learn people's names, call out to them, and then eat them. Meanwhile, the crowd in the hyena house starts to get rough with Lance, but suddenly their eyes start flashing yellow -- apparently, they've stepped into a mystical circle on the floor and a transformation has taken place. We see the eyes of one student who never meant to be there, and they're flashing yellow, too. It's Xander. Back at school, Principal Flutie proudly introduces the students to Herbert, the Sunnydale Razorbacks' new mascot. Not quite as menacing as the team's namesake, Herbert is a actually a little pig. Xander elicits a strange reaction from Herbert when the two exchange a glance. Since returning from the zoo trip, he is more confident, more aggressive, and generally not the same old Xander. His love-sick puppy stares have turned to animal leers -- he has even taken to sniffing Buffy. Willow brings the news to Buffy and Giles that Herbert is dead-- the pint-sized porker has been eaten by the hyena-possessed students. Buffy tries to confront Xander, but he becomes even more aggressive and pounces on her. They scuffle for a while, but Buffy finally decks him, and locks him into a steel book-return cage. When it is discovered that the pack is responsible for Herbert's demise, Principal Flutie is up in arms. He summons the group to his office to reprimand them, but doesn't get the chance. The news horrifies everyone -- Principle Flutie has been eaten! The "official" story is that a pack of wild dogs did it, but Buffy, Willow and Giles know the truth. Since Xander was with Buffy when the incident occurred, she is relieved that he was not involved. Giles has figured out that in order to restore order, the spirits of the hyenas must be taken from the students and put back into the animals. While Buffy and Giles go to the zoo, Willow offers to watch over Xander. The zookeeper, well-versed in these matters, offers to help with the "transformation," and says that all the students must return to the mystical circle in the hyena cage. But one member of their pack is missing -- Xander -- and Buffy and Giles realize, to their horror, that they will seek him out, leaving Willow vulnerable to their attack. When they do just that, Xander breaks free from the cage, but Willow hides. They escape the school grounds and Buffy leads them all to the zoo. While everything seems to be going according to schedule, it turns out that the zookeeper's plan is to absorb all the hyenaís spirits himself. He does, and grabs Willow in order to perform a predatory act which is part of the ritual. Xander, back to his old self, reacts to seeing his friend in jeopardy and dives on the zookeeper, freeing Willow. When the zookeeper goes after Buffy, she hurls him into the hyena cage, where he is promptly devoured.