The Hidden Valley
Thomsen, K. a.
Stacey and her best friend, country-wise Alexis, set out on a horse-packing trip through the Chilcotin mountains only to lose her beloved mare overnight. The clues lead them through a mysterious tunnel, which opens into a hidden valley full of prehistoric plants and animals. The mystery deepens when they are taken captive by a group of indigenous people that appear to be living a paleolithic lifestyle that has remained unchanged for centuries.