Glasswater Falls thundered behind us as we squeezed into the cave mouth. Three headlamps swung across wet limestone. Old Hennig's map promised a miner's vault down here, and there it was: a steel door, factory-gray, slick with damp. But the scratches around the lock looked fresh. Somebody had been here recently. "Guys," Priya whispered, "that's not rust."

Marco held up a hand. "Wait. Fresh scratches means someone's still down here." He clicked off his headlamp. We stood in the dark, listening over the roar of the falls. Then we heard it—boots on stone, somewhere deeper in the cave. Coming our way.

We ducked behind a boulder and waited. A figure in a soaked rain jacket stumbled past, mud-streaked and shaking. It was a kid, maybe our age, eyes wild with fear. "Don't go to the vault," he gasped to no one. "The floor—it gives way." Then he ran for the cave mouth and was gone.

We took the kid's warning seriously and roped ourselves together before entering the vault. Good thing—halfway in, a stone slab tilted under Priya's foot and dropped into darkness. The rope caught her. We pulled her back, hearts hammering. "Forget the gold," she said. We turned around and climbed out alive.