In a world where memories are tangible things, Hazel has always known one thing: a memory cartographer protects what others have lost. When memories begin vanishing from her town, Hazel discovers she's not the only one searching for answers. There's a False Echo who contains her mother's memories, a grandmother who trained the greatest cartographer ever known, and a villain whose plan has been forty years in the making. But when Hazel stops him, she learns the terrifying truth: she hasn't solved anything. She's only opened a door that should have stayed sealed. And something ancient is waking up.