Four years after 6-year-old Nathan Woessner got eaten by the Mount Baldy sand dune  in Indiana, the dunes are reopening. Nathan lived even after spending three-and-a-half hours trapped in a narrow hole, and geologists like Erin Argyilan have spent the last four years trying to work out what the hell happened.

Turns out “the entire dune had shifted 134 metres away from the lakefront between 1938 and 2007, swallowing up long-forgotten trees, trails and stairs along the way.”  As the sand-covered trees rotted over a seventy year period, “fungi on the covered trees formed a sort of cement that enabled the sand to keep its hollowed-out shape as the wood decayed and collapsed inward, leaving holes more than 10 feet deep in the dune.”

Tree-trunk-shaped hole, meet small boy. Voila,  a parents’ worst nightmare. My favorite part is Argyilan — who was actually there that day — not believing the parents when they said their son had been eaten by the dune, because science said sand dunes couldn’t be hollow. See, Nathan is an N of 1, and anecdotal experience is not evidence. Statistically, even now, no one has ever been eaten by a sand dune. Argyilan figured the kid was hiding.

After authorities recovered Nathan, still and cold and “gasping like a fish”, ground-penetrating radar found more than 60 spots where the sandy surface covered voids lurking beneath.

And now I’m wondering if there are any skeletons lying unsuspected inside the dune: very thin humans who took an unwary step and didn’t have doting parents as witnesses. One day the dune will move again, and we might all find out. And if you’re visiting the Indiana lakeshore, watch your step.