ECHO CHAMBER Intrepid visitors in Riverbend Cave, one of several caves you can explore at Vancouver Island’s Horne Lake Caves Provincial Park. WE WERE about 120 feet from the mouth of one of the caves in British Columbia’s Horne Lake Caves Provincial Parks when Ryan Nelson, our 29-year-old guide, suggested we find a stable perch on the water-slicked rocks beneath our feet. “In every cave,” Ryan told us, “you have the entrance zone, the twilight zone, and a zone where no light at all penetrates during a complete 24-hour cycle. Now, turn your lights off.” Desmond, my son, and I obeyed, flicking switches on our helmets. Suddenly there was nothing left in the world but the sound of a subterranean river rushing through limestone.

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