The House of Tunnels — Jerry B. Jenkins

Who would have guessed that the big old house holds such a secret? Not twelve-year-old Toby Andrews. And certainly not his deputy sheriff father. When Toby, his sister Kate, and the other Junior Deputies set out to explore Toby's new home, they find the totally unexpected--a secret passageway. Who put it there? And why? Toby and his friend Thomas decide to investigate further. And what they discover next puts them right in the middle of the police "sting" to trap a thief. Join Toby and his friends as they earn the title Junior Deputies.