Using clues from old books and hints from sad, restless spirits, Susan Olympia Slade, 14, solves a family mystery involving a missing girl, a dangerous boy, and a lighthouse on Prince Edward Island. Susan's SOS initials seem appropriate as she literally stumbles through middle school, uncertain about a body too mature for the rest of her. Then a relative dies, willing to Susan a lighthouse and a challenge: What became of her daughter, Emily Rose, who disappeared over fifty years ago? Accepting the challenge, Susan throws herself into the mystery, finding answers and, with them, a new sense of confidence.