The world isn't what it used to be. Generations ago, governmental experiments on the water supply had the unintended side effect of suppressing empathy in the population. While some retain a modicum of connectivity, those who, like Anathema, test highest on the Psychopath Scale, are recruited as an elite few who get funneled into boarding schools that direct their talents toward becoming assassins. If they survive the graduation ritual of Kill Slip Day, that is. 

With friendship a foreign concept and family only a vague idea from the time before the War, the only comforts Anathema knows are the pride she takes in her exceptionally deadly skills, and the few stolen moments in which she gets to unravel a long-gone student's hidden journal which she's discovered in her room. Within its pages, she finds the first fellow human she's ever related to: Mary. Mary's existence initially mirrors her own, despite the decades separating them, and Anathema's eyes are opened to a larger truth the more she follows Mary's journey. 

As the journal's mysteries seep into her reality, she draws the attention of some powerful forces at the school. Anathema becomes a valuable pawn in a larger game than she realized, and she starts to question the history she's been taught and the role in which she's been cast. Her budding desire for self-determination leads her to the recognition that the only way out is through the very bloody hurdles of her fellow assassins-in-training at the Prep School for Serial Killers.