Buffy the Vampire Slayer: False Memories

When Angel almost killed Dawn (Buffy's little sister), because no one had told her that he'd turned evil again? Buffy and the gang all have memories connected to Dawn, and only Buffy and Giles know they're not real. But there are still a lot of unanswered questions as to how Dawn came into Buffy's life, and where these memories come from.