I Will Remember You

After Angel's secretive visit to Sunnydale, Buffy appears in Los Angeles to find out why he came to protect her. During her visit, she and Angel are both attacked by a strange demon and Angel, after being infected with the demon's blood, becomes human once again. He and Buffy spend a blissful day together, but when the demon becomes more and more persistent in its attacks, Angel comes to realize that he must sacrifice his humanity in order to protect the citizens of Los Angeles.