Pretty Little Liars: Original Sin
Chapter Ten: Final Girls
S1 E10:
With the anniversary of Angela's death approaching, an already vengeful "A" doubles down. As Tabby and Imogen work to confirm a hunch, the members of the group confront their mothers about what really happened on New Year's Eve 1999 - and how it led to them being tormented in by a vengeful masked assailant in the present.