It's Oz's time of the month, which means he has to spend three consecutive nights locked in the book cage of the library while someone watches over him. After Xander comes in to relieve Willow of her post, he lies down on the table and falls asleep. At the cemetery, Buffy patrols for vampires with Faith. Neither of them are close enough to the woods to detect a chase, which ends brutally for a boy named Jeff Orkin. The next morning, Buffy, Willow, and Oz meet up with Scott and two of his friends: Pete and Debbie. Oz offers his old biology notes to Debbie, so they plan to meet up later. Buffy then heads off for her required therapy appointment with the counselor while Willow and Oz go to the library. To both Oz and Willow's dismay, Giles and Xander inform them of the murder that occurred the previous night. The fact that Xander slept through most of the night and the window inside the caged area is open does not bode well for Oz. Meanwhile, Buffy meets her counselor, Mr. Platt. While she's hesitant to discuss the full details of her reasons for running away, Buffy does come to respect Mr. Platt's helpful manner. After school, Buffy meets the others in the library and learns that Oz may have killed someone while he was a werewolf. Giles tells Willow, Xander, and Cordelia to go to the morgue and inspect Jeff's corpse, while Buffy must be on the look-out for the killer if it isn't Oz. He'll have Faith watch over Oz that night. At the morgue, Willow collects evidence which clearly indicates that Jeff was mauled by a savage animal. She then passes out due to the realization that Oz is the most likely suspect. Outside, Buffy encounters someone running wild through the woods.

To her surprise, that someone is Angel. However, he's not exactly in his right mind, and he immediately attacks Buffy. They fight for a while before Buffy finally knocks him out. She then takes him to Spike and Dru's mansion, where she uses some of Dru's old chains to lock Angel up and keep him from escaping out into the woods. Unable to communicate with Angel, Buffy notices the burnt pattern on the floor that indicates the spot where Angel landed at the end of his return trip from Hell. Unable to spend the rest of the night at home, Buffy goes to the library and takes over for Faith. Giles finds Buffy asleep in one of the library chairs the next morning. He notices the books she's been reading, which deal with demon dimensions and Acathla. After Buffy wakes up, she asks Giles if Angel could ever return from Hell, and if so, what would he be like. Buffy would rather not tell Giles right away that she found Angel. While Giles doubts the possibilty of Angel's return, he goes on to say that because time moves much faster in the other dimension, Angel would have been trapped there for an incredibly long time. After so many years of torture, he couldn't possibly be the same person mentally that he once was. Later, at lunchtime, Buffy joins Scott, Pete, and Debbie at their table. Unable to straighten out her feelings, Buffy leaves shortly and goes to the mansion. As soon as she rests a hand on Angel's shoulder, he goes berserk. Shaken by how much he's changed, Buffy heads back to Sunnydale High. Inside, Buffy goes to Mr. Platt's office and confesses that she truly needs help with all that's going on in her life. Unfortunately, she won't get any help from Mr. Platt, whom she soon discovers has been murdered, most likely by the same attacker that killed Jeff Orkin. After school, Pete pulls Debbie into the maintenance room to make out for a while. Inside, he notices that a jar once containing a glowing green formula is now virtually empty. Debbie tries to deny doing anything with it, but she soon admits that she got rid of it in order to help Pete get better. However, Pete convulses and transforms into a hideous, monstrous form of himself, proving to Debbie that he doesn't need the formula anymore. During this phase, Pete strikes Debbie in the face, knocking her to the ground. Pete then regains control of himself and changes back to his normal self before joining Debbie on the floor. Despite being struck by her boyfriend turned monster, Debbie has no problem excusing Pete's actions. Afterwards, Debbie meets Oz by the fountain to get his biology notes. Noticing the bruise on her eye, Oz stops Debbie from leaving right away by lightly grabbing her shoulder and asking if she's okay. From a distance, Pete watches this whole conversation. With evidence indicating that Mr. Platt was killed during the day, Oz is off the hook. In the library, the group draws a connection between the two victims and Debbie. Oz tells the others about Debbie's bruised eye, which doesn't quite follow with the suddenness of Mr. Platt's death. This leads them to suspect Pete, both for the two murders and for striking Debbie. While Oz locks himself in the cage for the third and final night of the month, Buffy and Willow confront Debbie. Unfortunately, Debbie refuses to help them stop Pete. During the conversation, Angel breaks his chains free of the mansion wall and escapes. Buffy and Willow have no idea that Pete is in the library at that very moment, ready to kill Oz for touching Debbie. Pete changes into his monster form and rips the door off the cage. After throwing Oz around the library for a little while, the sun finally sets and the moon shines, allowing Oz to turn the tables on Pete. In his werewolf form, Oz is an even match for Pete's ferocity. The sounds of their battle alerts the others to the library. Buffy tries to knock them out with the dart gun, but shoots Giles instead when Debbie pushes the gun off to the side just as Buffy pulls the trigger. While the tranquilizer dart takes Giles out of the action, Oz and Pete break apart and escape into the school hallways. Willow and Faith take down Oz with the dart gun. Buffy chases Pete to the maintenance room, where she finds Debbie dead on the floor, murdered by Pete. Another fight ensues. Just as it appears that Buffy's about to lose the fight, Angel arrives and kills Pete. To Buffy's suprise, Angel manages to say her name before falling to his knees and embracing her. The next day, Buffy can't find the words to console Scott, who lost two of his best friends without ever knowing the truth about what really happened. Later that night, Buffy watches Angel as he sleeps on the floor of the mansion. He constantly flinches and trembles, apparently suffering from nightmares of his time in Hell.