Jack and Annie have traveled all over the world in their magic tree house. But they've never been anywhere like this. In the distance, a haunted castle looms dark against the light of the moon. No candles burn in its windows. No laughter rings through its halls.
What has happened to the castle and the people who lived there? Merlin the magician asks Jack and Annie to find out. But are they brave enough to brush the cobwebs aside and step through the creaking doors? And are they smart enough to solve the mystery of how the castle became haunted?