Darla is introduced in "Welcome to the Hellmouth", the first episode of "Buffy the Vampire Slayer", in 1997. It is revealed early on that she is a vampire, initially in league with the Master, Buffy Summers' primary antagonist in the first season. Darla's backstory is disclosed in the episode "Angel", where it is revealed that she is Angel's sire (the one who turned him into a vampire) and former longtime lover. The character appears in numerous flashback episodes, until she receives a significantly expanded role in "Angel". In "Angel", she is resurrected by the evil law firm Wolfram & Hart in an attempt to weaken Angel. She later becomes intertwined in many of the story arcs in the second and third season. Darla becomes pregnant, a unique occurrence for a vampire. She sacrifices herself in order to give birth to her and Angel's human son Connor, ending her run on the series. However, Darla continues to appear in flashback episodes during the next two seasons.