Uncle Samuel had agreed, after years of turning down such requests, to let some spiritualist open the vacuus cubicularius at the core of the old house. Lucy had overheard her uncle and mother arguing about the wisdom of the plan -- her mother protesting that countless generations of owners had forbidden any entry into that chamber, and Uncle Samuel overriding her objections with condescending skepticism and reminders of a promised ten thousand pounds.

Lucy had sometimes, late at night, padded with a candle all the way down the oldest hallway and touched the corroded iron door in the ancient masonry. The story as she had gathered it was that the chamber had been built nearly a million years ago by Neanderthals or Ancient Britons, and had originally borne an inscription in some primordial script stating that no human had ever set foot on the ground enclosed in it. It had stood as an isolated stone building in a field for centuries, preserved by a succession of secretive owners; eventually London had engulfed it, and house after long-standing house had been built over it. Its present iron door had supposedly been bolted onto the stone in the 12th century, right on top of a previous very old wooden one, which in turn would have been only the latest in a series of them.

In her midnight visits Lucy had even pressed her ear against the ancient iron surface, but had heard only her own pulse rung back at her. Once, she had worked up the nerve to knock on it, but her little knuckles produced no sound at all. The only time she had seemed to get a response was so long ago that she wasn’t sure she hadn’t dreamed it -- after pressing her palm against the door, the cold corroded iron had shivered in a faint but rapid rhythm, as if with the rushing footsteps of a giant still very far away. She had scampered back to her bed, and only in the morning assured herself that it must have been the reverberations of a heavy wagon making its way along the street.