by Gertrude Chandler Warner (Created by)

The Boxcar Children are visiting Dragon Mouth's Cavern. Their plan is to explore the area and go rock hunting. But when Benny finds a way into secret underground caves, the children have even more to explore. The problem is, it seems like someone doesn't want them there. Can the Aldens solve this underground mystery?

Front Jacket

When the Aldens' explore Dragon's Mouth Cavern, they encounter some suspicious people.