I love mysteries, whether they unfold on the page or echo from a craggy rock formation in the high desert of southwestern Colorado. Crisp, fall air drew me to the twin peaks of Chimney Rock National Monument last fall, during a road trip through New Mexico and Colorado. After clambering up the steep trail to the top for a 360-degree view of the San Juan Mountains, I was captivated by the legends linking this isolated outpost to the ancient Chaco culture. Ancestral Puebloans, as they...