'Twist follows twist and nothing is what it seems' ALEX MICHAELIDES'Exhilarating, addictive, fierce' BRIDGET COLLINS'A psychological thriller you can't put down' HARLAN COBEN'Dark, Gothic, and propulsively readable' RUTH WARE'A dark and richly enjoyable novel that already feels like a classic' ELLY GRIFFITHS* * * * *Now I'm in charge, the gates are my gates. The rules are my rules. It's an incendiary moment for St Oswald's school. For the first time in its history, a headmist