Now that they are seniors, the gang can leave the Sunnydale High campus for lunch, which they do. Lunch is a picnic with Buffy, who is longing to get back to her normal life - shopping, hanging out, going to school, and saving the world. Maybe even dating, as Willow points out a boy named Scott Hope, who's liked Buffy since last year. Buffy seems reluctant. That night, there are some new arrivals in Sunnydale: a limo pulls up to the local Happy Burger. In the back is a black vampire named Mr. Trick, who is positively salivating over the prospects that Sunnydale presents, and his cloven-hoofed master who has but one thing on his mind: killing the Slayer. Buffy has another disturbing dream about Angel and how she killed him to save the world. That morning Principal Snyder is forced to readmit her to school on the condition that she takes makeup tests and gets a psychologist to see to her violent tendencies, and Buffy and her mother leave his office in triumph just as the Mayor calls. Later, Willow and Buffy go to the library, where Giles tells Buffy that he's casting a binding spell to make sure that Acathla, the demon Buffy killed Angel to stop, is truly bound, and he needs some details about how she stopped the demon. Buffy provides them, briefly, then runs off to a test as Willow accidentally reveals her dabbling in witchcraft to Giles. That night at the Bronze, Buffy is happy about having her life back, but is again hesitant when Scott Hope shows up and asks her to dance. Then Cordelia points out that the date of a striking girl on the dance floor is a throwback to the 70's. As the girl and her date leave, Buffy gets a feeling he's a vampire and follows them. They find the girl kicking the snot out of her date who, as Buffy thought, is a vampire. "I'm gonna go out on a limb and say there's a new Slayer in town," says Oz. There is a new Slayer, called upon the death of Kendra. Her name is Faith, and she quickly charms Buffy's friends with her wild Slaying stories. She even wins over Giles, who tells the two Slayers about missing people on Sunset Ridge. Buffy says she and Faith will patrol (after reluctantly inviting Faith to dinner with her mom), and then her friends run off with Faith. Buffy is not happy about the whole thing, and again gives short answers when Giles requests details about her experience with Angel and Acathla so he can cast the binding spell. Faith comments to Willow and Xander about Buffy's down attitude, and then Buffy arrives to see Faith flirting with Scott Hope. Meanwhile, Mr. Trick just loves Sunnydale for its high-tech possibilities, but his master is still only interested in killing the Slayer. When Trick points out that Sunnydale already has a Slayer, it becomes clear that they came in pursuit of Faith. The cloven-hoofed master points to his destroyed right eye, saying, "She's going to pay for what she did to me." That night, even Joyce is completely taken with Faith. When Joyce suggests that Buffy could just let Faith take over as Slayer, Buffy exasperatedly lets slip that a new Slayer can only be called when the old one dies. Joyce is devastated to find that Buffy died, even for a moment, but Buffy comforts her. Later, Buffy and Faith argue while on patrol when Faith nonchalantly mentions Angel. They're about to fight each other when a group of vampires shows up. Faith is just hitting one repeatedly and not staking him. Buffy yells at her to help, but then gets pinned by a vampire who says, "For Kakistos we live, for Kakistos you die." Buffy manages to kill her vamps, and the one that Faith was hitting too, but when she confronts Faith about her behavior, Faith lightly blows it off. Buffy complains about the incident to Giles the next day, and he promises to call England and ask her Watcher. Then Buffy mentions Kakistos, and Giles is disturbed. Kakistos is a very old vampire, and Buffy guesses he followed Faith to Sunnydale. As she goes to ask Faith about it, she runs into Scott Hope, who invites her to a Buster Keaton film festival. Buffy brightens and accepts his offer, but then he gives her a claddagh ring and memories of Angel come flooding back. She drops the ring and nearly bursts into tears, scaring Scott off. Then Giles shows up with more bad news: Faith's Watcher is dead. That night Buffy goes to Faith's motel room and confronts her about Kakistos and her Watcher, and Faith angrily says she can deal and prepares to leave again. A knock on the door appears to be the motel manager, but when Faith opens the door, the manager's dead... and there stand Kakistos, Trick, and a whole bunch of vampires. The two Slayers run, but the vampires herd them into their hideout. Faith reveals that she saw what Kakistos did to her Watcher and she ran, but Buffy reassures her she did the right thing, just as the vamps show up and a fight ensues. Buffy takes on several vampires, but Faith freezes before Kakistos, who has her at his mercy. Buffy intervenes, and seems to be beating Kakistos. Mr. Trick, citing "the big picture," takes the other vampires and leaves. When Buffy's normal-sized stake isn't enough to finish Kakistos off, Faith comes to and shoves a massive wooden pole through the ancient vampire, finishing him for good. The Watcher's Council agrees to have Faith stay in Sunnydale indefinitely under Giles' care until a new Watcher is assigned. Buffy, inspired by how Faith dealt with her issues, reveals to Willow and Giles what really happened the night she killed Angel - how he was Angel again before she kissed him and killed him. Feeling better she walks off (as Giles tells Willow the "binding spell" was just a ruse) and takes Scott Hope up on his date offer once and for all. That night she goes to the mansion where she killed Angel and, placing the claddagh ring Angel gave her on the ground, quietly says, "Goodbye." After she leaves, though, a bright shaft of light illuminates the ring, and a naked Angel falls out of the light to lay on the floor, sweaty and trembling.

It's that time of month again, and Willow turns the job of watching Oz (who is in full werewolf form and locked up in the library's book return cage) over to volunteer Xander... who promptly lays down and goes to sleep. On patrol, Faith shares with Buffy her conviction that all men, no matter how sensitive they may act, are beasts deep down inside. And, unobserved by the two Slayers, a young man named Jeff Walken runs through the thick foliage, but falls, screaming as his unseen pursuer overtakes him. The next day at school, Buffy runs into Scott Hope, and all seems well as they hang with Scott's friends Debbie and Pete, a couple. They discuss Mr. Platt, the school counselor, with whom Buffy has an appointment and who Debbie has to see because she's failing senior biology. Oz offers his notes from that class as Buffy goes to keep her appointment, kissing Scott goodbye. Oz and Willow go to the library to see Giles extremely agitated. Walken, a friend of Oz's, was found mauled to death in the woods, and Giles has to entertain the unappealing possibility that it was Oz. Xander protests that it couldn't have been, since he was there all night and he only "rested his eyes" a few times. Everyone knows the truth, even Xander, as he tries to joke away Giles' anger. And to make matters worse, the window in the book cage is open. Both Willow and Oz are quite upset. Buffy keeps her appointment with Mr. Platt, who kindly but firmly asks about why Buffy ran away. Buffy glosses over the details of her relationship with Angel, and Mr. Platt tells her that one can't stay lost in love forever, or else "love becomes your master... and you're just its dog." A troubled Buffy returns to the library to find everyone moping over the possibility that Oz killed someone, but she rallies the troops to action. When they suggest that Faith watch Oz that night, Oz gets upset and tries to leave, but it's too close to sundown, so he unhappily slouches into the book return cage. That night on patrol, Buffy sees something running through the trees. She gives chase and it knocks her down, but when she gets up she sees her assailant and her eyes go wide - it's Angel! They fight, and Buffy manages to knock Angel out. At the morgue, Xander and Cordelia freak out at the sight of Jeff Walken's hideously mauled body, but Willow cold-bloodedly collects the necessary evidence... and then faints. Buffy takes Angel back to the mansion and chains him up. He's feral and animalistic, nothing like the Angel she knew. And there's a burned-in impression of his body on the floor where he came back. Buffy heads back to the library and relieves Faith on Oz-watching duty, and as soon as the other Slayer leaves she starts in on the card catalog. Giles arrives in the morning to find both Oz and Buffy asleep. Buffy has been reading up on some pretty heavy stuff, and after he pries a little she tells him she dreamt that Angel returned. She asks him if it's possible for someone to return from the demon dimension, and what Angel would be like if it was. Giles' answers are not encouraging to her. Willow arrives with doughnuts, but is cagey about what she found at the morgue. Buffy's too-intense questioning of Willow makes it clear: Buffy thinks Angel could be the killer. The prospect bums her out all day, and lunch with Scott, Debbie and Pete is a somewhat morose affair despite Scott's sweet attempts to joke her out of it. She runs off and heads back to the mansion where she asks Angel if he can understand her. He doesn't respond, and lashes out like an abused dog when she tries to touch him. Even more upset than before, Buffy heads back to school. She barges into Mr. Platt's office and starts to tearfully spill about Angel when she notices Mr. Platt's cigarette burned all the way down to the filter in his hand. He's dead, mauled terribly. Pete talks Debbie into a storage closet for some make-out time, but gets upset when he notices an almost-empty jar of some green liquid. Debbie protests that she was just trying to get rid of the stuff because of what it does to Pete, but he only gets angrier, saying it's not the green liquid that does it, it's her. With that, he changes into a monstrous verson of himself and starts hitting Debbie, telling her that Mr. Platt won't listen to her whining any more. Suddenly, he seems to come to his senses, and his face returns to normal. He rushes to Debbie, hugging her and telling her he's sorry. She tells him it's okay. At the library, everyone's a little happier because the coroner's conclusion that Mr. Platt was killed during the day lets Oz off the hook. However, it's almost sundown and Oz isn't there. He's meeting with Debbie to give her his senior biology notes, and he notices she's sporting a new black eye. Debbie dismisses his concern as Pete watches from afar. Oz returns to the library and, upon hearing the evidence, realizes that the link between the two victims is Debbie. They conclude that Pete could be the killer, and everyone goes off to find Pete and Debbie while Oz locks himself in the cage. At the mansion, Angel breaks free of his chains and runs off. Buffy and Willow find Debbie in the bathroom trying to cover up her black eye, and they confront her. She lets slip that Pete is the culprit, but blames herself, saying she's what makes him angry. Buffy angrily confronts her, saying two people are dead. "Who's gonna be next?" she asks. It would appear to be Oz, who is locked in the cage as Pete shows up. He accuses Oz of putting moves on Debbie, and Oz's warnings about what's gonna happen when the sun goes down are cut off when Pete's monstrous alter ego comes out. Pete rips the door off the cage and starts to brutalize Oz, but then the sun sets, and Oz changes into a werewolf. Suddenly the fight is more even, and Oz bites Pete, whose scream brings everyone to the library. Buffy grabs the tranquilizer rifle and is about to fire, but Debbie shoves her so the dart goes into Giles, who collapses. Oz escapes, pursued by Faith and Willow, while Buffy chases Pete off. Pete escapes and meets Debbie in the storage closet. Debbie tells him to leave Sunnydale because Buffy knows, but Pete is enraged and accuses Debbie of telling. Meanwhile, Faith and Willow manage to shoot Oz with the tranquilizer rifle. Buffy tracks Pete to the storage closet, where she finds Debbie dead. Then Pete attacks, but their fight is interrupted by the arrival of Angel. In full vampire face, Angel attacks Pete, and kills him. As Buffy watches, Angel's face reverts to normal. "Buffy?" he asks shakily, hugging her as Buffy starts to weep. The next day stories of what happened are all over school, but Willow knows the truth: Pete originally made the formula to be more macho for Debbie, but eventually didn't need the formula to change. Buffy comforts Scott, who is shaken by the deaths of his lifelong friends. "It's just that you never really know what's going on inside somebody, do you?" he asks. Buffy contemplates that later as she watches a trembling Angel sleep.