Puzzle

The desertlike plain stretches forever before Devon Adair and her companions. It is rugged, desolate, quiet. Until the thunder starts...a thunder caused by a vast, violent herd of buffalo-like beasts. The reluctant colonists fight to keep from being trampled and losing the last of the their already dwindling supplies.

And when the dust finally settles, they make an amazing--and dangerous--discovery. The entrance to a massive underground city.

Earth 2: Puzzle