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."

I grabbed the door handle and pulled. It groaned open an inch, then stuck. Cold air hissed out, smelling of metal and old dust. "It's not even locked," I said. Marco and Priya leaned in beside me and we heaved together. The door swung wide into the dark.

Inside, our lights found shelves of dynamite crates, rusted tools, and a single iron strongbox on a table. Marco lifted the lid. Gold coins glinted, plus a leather journal. "Hennig was telling the truth," he breathed. Then the door behind us creaked—and slowly began to swing shut on its own.

We read the journal by headlamp before leaving. Hennig hadn't just hidden the gold—he'd hidden it from robbers, and the last page warned the door was rigged to trap anyone greedy. "Leave the coins," I said. We set the box down, kept the journal, and walked out free. Some treasures aren't worth the door.