Thirteen-year-old Kasey Madrid finally has the freedom she's always wanted. Instead of putting up with sitters or camps, she can spend the summer home alone in their "new" house. Never mind that the house is a creepy old place built in the nineteenth century. The creep factor skyrockets when Kasey meets a nineteenth-century girl named Lizzie Bellows in the basement. It takes some time for Lizzie to convince Kasey she's not a ghost, though neither girl understands why they can see each other when they live 120 years apart. The difference in their worlds doesn't stop the two from becoming fast friends. Lizzie's life isn't easy though. In her time, her parents died in a fire many believe Lizzie started herself. As the summer passes and Kasey learns more about her own past, she is shocked to discover Lizzie is part of a terrible Madrid family secret. It's up to Kasey to go back to Lizzie's world to unlock the secret and clear Lizzie's name.