The Crystal Doorknob — Catherine George

Miley and her cat Oscar embark on an adventurous journey into another world with the help of a magical crystal doorknob. The house Miley lives in was part of the Underground Railroad, where many years ago her great-great grandfather helped slaves escape to freedom. What he didn't know was that the secret passage led to another world where they established a whole new society. Miley stumbles on the secret doorway and her curiosity gets her and Oscar into all sorts of trouble.