The Secret of the Silver Key is the second book in the Fribble Mouse Library Mysteries Series. Fribble and his little brother, Scamper, live in Cheddarville. Fribble has both extraordinary whiskers and an extraordinary curiosity. This curiosity is aroused when he receives in the mail a birthday card from his grandparents that contains a silver key. Not wanting to wait for his birthday and the gift awaiting him, Fribble tries to learn what the key might unlock. Once he learns that, he finds himself facing another mystery. Where will it lead him? Only the library can help him solve the secret of the silver key.