Angel: Season 1, Episode 8
I Will Remember You
Buffy arrives in L.A., furious that Angel did not tell her that he was in Sunnydale. While they are talking, they are attacked by a Mohra demon, and some of its blood gets onto Angel. After a brief hunt, they kill the demon, but its blood is having a strange effect on Angel. He feels short of breath, dizzy, and disoriented, and then suddenly his heart begins to beat. Now fully human, Angel must decide how this will affect his relationship with Buffy and whether or not he can still be a Champion.