Who do you trust when you can no longer trust your own mind? A state school girl at a prestigious music school, Emma is determined to excel. Then the impossibly chic twins, confident Sophie and quieter Matilde, come crashing into her life. Surrounding her with champagne and parties, they demand Emma's full attention. Struggling to balance it all, the girls are plunged into insomnia and bitter rivalry. And then shy Matilde commits suicide. Shockingly, her identical twin Sophie flourishes even more. But strange things are happening to Emma: missing time, waking up in strange places, bizarre dreams. Something, or someone, is consuming Emma's mind. Terrified, Emma begins to doubt everything and everyone around her, especially the beautiful Sophie...