Sage Winters always knew her sister was a little different even though they were identical twins. They loved the same things and shared a deep understanding, but Rosemary-awake to every emotion, easily moved to joy or tears-seemed to need more protection from the world. Six years after Rosemary's death from pneumonia, Sage, now sixteen, still misses her deeply. Their mother perished in a car crash, and Sage's stepfather, Alan, resents being burdened by a responsibility he never wanted. Yet despite living as near strangers in their Staten Island apartment, Sage is stunned to discover that Alan has kept a shocking secret: Rosemary didn't die. She was committed to Willowbrook State School and has lingered there until just a few days ago, when she went missing. Sage knows little about Willowbrook. It's always been a place shrouded by rumor and mystery.