What if the dinosaurs had never become extinct?

When an earthquake opens a temporary portal into an underground world, four teenagers at summer camp discover that dinosaurs did not die out and have evolved into intelligent life beneath earth.

Now they're back...

What does their re-appearance have to do with Lauren's dad, who vanished on a fossil expedition, and Kit's mysterious Uncle Ten Bears, a Native American medicine man who knows more about the dinosaurs than he's letting on?

This edition includes the exciting first series.