A strange tunnel. Ten riddles. Can you solve the case and return a fortune? It's a beautiful summer day, and Leo, Mara, and Mara's dog Snowflake are headed back to acrobatics camp near old Volkenstein Manor. But on their way, the group stumbles upon a freshly dug tunnel that leads...to a bank vault?

The kids find themselves in a mystery that keeps getting stranger. Soon they are investigating the theft of the Volkenstein family treasure and pursuing a gang of robbers. But they won't succeed without your help!