In this thrilling volume of the action-adventure series for younger readers, the group of pals known as the Border Boys find themselves in hot water when their exploration of the open range leads them to a mysterious underground river. It's not only a wonder of nature—it's also a conduit for illegal activities, as the boys soon discover.
- New kids additions
- New teen additions
- Available now
- Book Club Picks
- Series Starters
- Most popular
- Try something different
- Learn Something New By Reading Something True!
- New Book Arrivals
- Most Popular eBooks
- Improve Yourself!
- Get Clean & Organized!
- April is National Poetry Month!
- See all ebooks collections
- Available now
- New audiobook additions
- Audiobooks for your Commute
- Popular Audiobook Narrators
- New kids additions
- New teen additions
- Most popular
- Try something different
- Presidential Lives
- I Heard It On The Radio
- New Audiobook Arrivals
- Women Making a Difference
- A Listening Buffet
- See all audiobooks collections