The night before a full moon, Willow reads from "Call of the Wild" to an agitated Oz locked up in the library cage. Xander shows up for the second shift -- or rather, snoozing. Meanwhile, Faith and Buffy are making a sweep around Sunnydale. Faith displays a cynical view of males, while Buffy dodges her questions. They talk about Scott and how much Buffy likes him, but is still planning to take it slow on account of her previous history with men. A boy is attacked brutally in the woods.
The next day, Buffy talks to Scott and his friends, Debbie and Pete, who are a couple. Buffy reveals that she has to see Mr. Platt, the school psychologist. Debbie sees him, too, for "success issues". Buffy kisses Scott goodbye and leaves for her appointment.
Xander and Giles find out about the murder the night before. They discover that Xander slept through his watch and that the window in the pen is open. Everyone is horrified that Oz may have escaped and killed someone.
Buffy talks to Mr. Platt about her life as vaguely as she can about her life with Angel. She finds in him an understanding figure -- unlike Debbie's description -- and begins to open up. She seems to be on her way to resolving her issues, but on patrol that night, Angel tackles her in the woods. Animalistic, he is no match for Buffy, who chains him up in the mansion. He growls at her like an animal. She discovers the spot on the floor where she left his ring; it was scorched by Angel's body on his return.
At the same time, Willow, Xander and Cordy enter the morgue to inspect the mauled body. Willow seems the only one unfazed, but she faints after collecting hair samples.
With everyone else unavailable, Faith stays in the library with Oz. Buffy comes in and receives a hard punch for startling her. Buffy sends Faith away and spends the night searching for answers about Angel's return. The next morning, Giles finds her asleep around books about demon dimensions and Acathla. She tells him she had a vivid dream that Angel came back. Giles explains that time passes differently in Hell (as Buffy found in episode 'Anne'), so any being who manages to return would most likely become a monster, if it can be done at all. It would take extraordinary character to remain any semblance of self. Willow arrives to inform them that her investigation was not conclusive. Buffy is anxious as she wonders if Angel was responsible.
In the cafeteria, Buffy sits with Scott, whose mother is insulted by Pete along with the school counselor. Buffy decides to leave for the mansion, where she finds Angel huddled in a ball. She tries to touch him, but he jumps at her. She rushes out, scared.
Pete and Debbie sneak into a room to make out. Pete discovers that one of his jars has been emptied and accuses Debbie of drinking its contents. Buffy returns to Mr. Platt's office and pours her heart out, then realizes that he has been mauled to death.
Pete yells at Debbie, then turns into a monster with very noticeable veins. He tells her that he needed the substance to turn into the monster, but now only needs to get mad. Acting in a manner similar to steroid rage, he begins beating Debbie, then apologizes, turning back into his human face. She forgives him. It is clear that Pete is a domenstic abuser and Debbie is too emotionaly broken to tell anyone.
In the library, Oz and Angel (who Buffy has not informed the gang of) are cleared. The Scoobies must look for a murderer who kills during the day.
Oz meets up with Debbie and gives her his study notes as promised. He notices her black eye, but she lies to Oz, telling him she fell on a doorknob. He lets her know he will listen if she decides to talk. Meanwhile, Pete is watching and seething.
The gang have discovered the killer, and they leave Oz in the library to look for Pete and Debbie. Buffy and Willow find Debbie in the girls locker room and try in vain to talk sense into her at how Pete is killing people, but Debbie foolishly tries to defend Pete and his actions that "he only gets angry sometimes". Meanwhile, Angel breaks free from his shackles, and Pete finds Oz in the library. He turns into a monster and beats up Oz. Then the sun sets, and Oz becomes a werewolf. Buffy and the rest of the gang arrive to stop the fight, but when Buffy tries to tranquilize Oz, Debbie deliberately pushes her gun away and Buffy ends up shooting Giles. Buffy chases after the monster Pete while Willow and Faith follow the werewolf Oz.
After a struggle, Faith manages to hit and knock out Oz with a dart. Buffy follows Pete's blood trail, but he finds Debbie first and despite her pleas and her attempts to appease him, he kills her. Buffy finds Pete, but he knocks her to the ground and advances threateningly on her. Angel arrives on time and he and Pete begin fighting; after knocking Angel aside, Pete turns his attention back to Buffy, but Angel gets back up and, using the chains still binding his wrists, snaps Pete's neck, killing him. Then he reverts to his human face and calls out Buffy's name. They cry as Buffy becomes more confused than ever.
The next day, it is revealed in detail by Buffy that Pete had concocted a chemical potion that turned him into Mister Hyde-type "Lance Macho" when he became afraid of losing Debbie, but eventually he became monstrous himself due to his repressed misgynostic rage. Buffy tries to console Scott, who has lost two of his best friends and didn't know about Pete and Debbie'e true nature. Buffy visits the mansion, where Angel sleeps through an apparent nightmare unshackled. The episode ends with Buffy reading from "Call of the Wild".