The Haunted Key (Frightville #3)

Welcome to Frightville... one-stop shopping for all your fears! When Sofia buys a cool skeleton key from a creepy store, Frightville, it quickly becomes her favorite possession. It seems to open any lock she tries it on - even the rusted old lock on the attic in her new house.But opening that door seems to have magically opened a door into the past. A past that Sofia starts to think should have stayed locked up.