Sonder (noun):

The realization that each random passerby is living a life as vivid and complex as your own.

Allegra has never been exactly normal. She's never had any friends, but that's never bothered her. She has acquaintances on her high school's dance team, and she can get pretty much anything she wants out of boys, but what she really wants is to watch someone's life leave their body, exhaling their last breath.

Robin has fallen for Ally, fast and hard. Even though they agreed to move in together as just friends, she can't stop her feelings. She'll do whatever Allegra wants...from breaking up with her boyfriend to planning something sinister.

They have the perfect plan. But when Allegra's mother starts to piece things together, it just takes a little manipulation to put everything into a whole new perspective.