Season 1 Episode 07 - Angel
On her way home from the Bronze, Buffy encounters three vampires, who've been sent to avenge the death of one of the Master's minions. Just as they're about to attack her, Angel appears and they begin to fight. Angel and Buffy manage to make it safely to her house, where she repairs the wound he got in the scuffle. He spends the night in her bedroom, sleeping next to her bed. The next day at school, Giles identifies Buffy's attackers as warrior vampires, and steps up her training in case a more serious melee takes place. Later that day, Buffy and Angel share a passionate kiss, but then to her horror, she sees that he is a vampire!
Angel meets up with Darla, who was his lover and partner in crime hundreds of years earlier. She chastises him for spending time with the Slayer. Meanwhile, Giles identifies Angel as a 240-year-old vampire who came to America 80 years ago, living alone and never killing again. Darla, anxious to do Buffy in, goes to her house and pretends to be a student planning to study with her. Buffy's mother, Joyce, lets her in and Darla promptly bites her in the neck. Angel enters the house and tells Darla to let Joyce go. Darla passes Joyce to him and he is tempted to bite her, but doesn't. When Buffy enters, she sees Angel holding her mother and, assuming he is the one who bit Joyce, she tosses him out the window. This finally gives her the impetus to kill him, and she meets him at the Bronze with a crossbow. He explains that he did many heinous things over the course of his lifetime, but his soul has been restored by a gypsy curse and he is now haunted by them. Darla finds them together and tries to shoot Buffy. Angel impales Darla from behind and she turns to dust. When the Master finds out that Darla, his favorite, has been slain, he goes berserk, but the Anointed One comforts him.
Back at the Bronze, Angel and Buffy agree that despite their strong feelings for each other, it's not realistic for them to pursue any kind of relationship. They kiss goodbye and when Buffy walks away, the imprint of her cross has been seared into Angel's chest.