The Aldens are off on another adventure---this time, Grandfather is taking the children to a castle! The Aldens have offered a friend to help clean up an old castle and help to restore it before it is made into a museum. But strange things begin to happen and the kids start to wonder if there is a ghost! Can the children solve the mystery hidden within the castle's walls? This book is number 36 in the series.
Grandfather's friend, Carrie Bell, is restoring an old castle. She invites the Aldens to help out. The children can't wait to stay in the castle, especially when they learn about the mystery of the missing Stradivarius violin.