With dismay the old man watched the arm of water through which he plodded swell and send out tendrils of its own. It was almost up to his calves now, and the leading edge rolled onward, pulling maddeningly away from him as he dragged himself towards it. His heart pounded with each lurching step through the sucking sand, and he was hot and fearfully cold at the same time. Icy water began slopping onto the tops of his boots, weighing him down still more and setting his limbs to convulsive shivering.

The boots, he thought. If he could get them off…But he knew he couldn’t afford to stop in the rising water, and he knew he didn’t have the strength to do it; not with only one good hand. In growing confusion he tore off his fur hat instead and threw it away. The chilling blast of sleet on the back of his neck made him cry out and tremble so convulsively that he could barely see. Still, with the water sloshing in his boots and his breath like knives in his throat, he managed three more blind steps before he finally stumbled into the quicksand.

The infamous sable mouvant of Mont St. Michel Bay is not quicksand, strictly speaking, not a slippery, shifting mass of smooth-grained sand and upward-percolating water; it is a phenomenon unique to this colossal tidal flat: deep pockets filled with water and covered with a layer of sand that somehow floats on top of them. From the battlements of the north tower they are invisible, and to the small, avid crowd gathered there it seemed as if the legs of the staggering man on the darkening plain below suddenly disappeared. A woman screamed and locked her fingers over her mouth. The others watched in rapt, shocked silence. Below, the tiny figure struggled, flailing at the still-shallow water with one arm and sinking all the more rapidly for it.

Until the very instant it closed smoothly over his head he was wriggling so desperately it seemed he must come up again, but the surface remained unbroken except for an innocuous dimple that marked the place he had been. And within a few seconds it was as if he had never been there at all.