Sixteen-year-old Lil's heart was broken when her sister, Mella, disappeared. There's been no trace or sighting of her since she vanished, so when Lil sees a girl lying in the road near her house, she thinks for a heart-stopping moment that it's Mella.

The girl is injured and disorientated and Lil has no choice but to take her home, even though she knows something's not right. The girls claims she's from a peaceful community called The Sisterhood of the Light, but why then does she have strange marks down her arms, and what - or who - is she running from?