On prom night, Hannah MacLaren sits in the headmaster's office in her fanciest dress, soaked to the bone. She is in huge trouble after pulling the fire alarm right as the prom queen was about to be crowned. But Hannah had her reasons . . . One year ago, her cousin Sophie, who was also her best friend and the person she loved most in the world, died of an overdose. Drowning in grief, Hannah became obsessed with one question: Who gave Sophie those pills? Who is refusing to give her family the closure they deserve? Then she concocted a plan: enroll at her cousin's fancy private school with a new look and a mouthful of lies, and finally uncover the truth. But Hannah didn't expect all the lines to blur. She didn't expect Sophie's friends to be so complicated. She didn't expect to fall for her longtime enemy. Now, she must choose to either let herself really mourn Sophie and move on, or see her search through to its explosive end—even if it means destroying herself.