The Sanctuary meets Shutter Island in this high-concept psychological thriller from the critically acclaimed author of The Sisterhood.Birds of a feather   A group of teenagers jump off a train platform intentionally into the path of an arriving train. The lone survivor, Charlie, cannot recall the incident, but is adamant that she and her friends weren’t suicidal.    Flock together . . .   Her mother, Jo, is desperate for answers. When she’s approached by Nathalie Bergstedt, the Director of the Arbor Institute, a government-affiliated research institute who are investigating the rise of ‘flock’ behaviour phenomena – where people are banding together to self-destruct – she agrees to take Charlie there.  But never underestimate,   At the Arbor Institute, Charlie is told that she’s at risk of ‘re-flocking’ and if she does, she will likely die. But when another flock-survivor disappears and Charlie discovers that she’s being watched, she realises that not everything is as it seems at the Institute. But as everyone knows, nature is red in tooth and claw and you should never corner a wounded animal.  The instinct to survive. . .