The Sanctuary meets Shutter Island in this high-concept psychological thriller from the critically acclaimed author of The Sisterhood.BIRDS OF A FEATHER FLOCK TOGETHERBUT NEVER UNDERESTIMATETHE INSTINCT TO SURVIVEA group of students jump off a train platform into the path of an arriving train. The lone survivor, Billie, cannot recall the incident, but is adamant that she and her friends weren't suicidal. Desperate for answers, Billie agrees to sign herself into the care of the Arbor Institute, a mysterious, corporate-backed research body investigating a disturbing rise in similar incidents around the globe.At the Institute, Billie learns more about 'flock phenomena', where people band together to self-destruct. She is told that she's at risk of 're-flocking', and if she does, she will likely die.But not everything is as it seems. When Billie discovers that she and her fellow survivors have been completely cut off from the outside world, she realizes they may not be safe.And as she sets her sights on survival, the Institute may regret taking her under their wing. Because this wounded fledgling might turn out to be a bird of prey...