We'd spent the morning driving across southern Idaho's high desert, where miles of open country stretch beneath an endless sky. Sagebrush rolled past the windows in muted shades of green and silver, and the horizon seemed to breathe in slow motion.

The smell was unmistakable: rotten eggs, sulfur heavy and sticky in the air. We pulled off the narrow track, dust settling behind us like a curtain, and Dan popped the hood. Everything looked normal, yet the odor lingered. That’s when Tara pointed off to the right, where the ground cracked open like a secret waiting to be told.