Winter and Arden Allister are two teenage sisters who've just moved from Memphis to San Francisco and their interracial family is thrust into the bourgeoisie of San Francisco's elite once the girls begin the year at an exclusive private school. But when Winter starts having problems with a boy at school and Arden continues to suffer inexplicable and terrifying blackouts, each girl must tease loose a separate thread of fate from their interwoven, close-knit identity as sisters in order to unravel the arcane mystery of who they really are. Once their futures are disentangled, Winter and Arden find that destiny has drafted them both into the oldest war the world's ever known-but placed them on opposite sides.