Polly lives in a house bursting at the seams with people, while Rose is often left alone by her busy parents. Polly is a down-to-earth dreamer with a wild imagination and an obsession with ghosts; Rose is a quiet, ethereal waif with a sharp tongue. Despite their differences, both girls spend their days feeling invisible and seek solace in books and the cozy confines of their respective attics. But soon they discover they aren't alone--they're actually neighbors, sharing a wall. They develop an unlikely friendship, and Polly is ecstatic to learn that Rose can actually see and talk to ghosts. Maybe she will finally see one too! But is there more to Rose than it seems? Why does no one ever talk to her? And why does she look so... ghostly? When the girls find a tombstone with Rose's name on it in the cemetery and encounter an angry spirit in her house who seems intent on hurting Polly, they have to unravel the mystery of Rose and her strange family... before it's too late.