Denis breathed again. He gave them a few minutes' grace for fear of accidents, and then groped about for some means of opening the door and slipping forth again. The inner surface was quite smooth, not a handle, not a moulding, not a projection of any sort. He got his finger-nails round the edges and pulled, but the mass was immovable. He shook it; it was as firm as a rock. Denis de Beaulieu frowned and gave vent to a little noiseless whistle. What ailed the door? he wondered. Why was it open? How came it to shut so easily and so effectually after him? There was something obscure and underhand about all this that was little to the young man's fancy. It looked like a snare; and yet who could suppose a snare in such a quiet by-street and in a house of so prosperous and even noble an exterior? And yet--snare or no snare, intentionally or unintentionally--here he was, prettily trapped; and for the life of him he could see no way out of it again. The darkness began to weigh upon him. He gave ear; all was silent without, but within and close by he seemed to catch a faint sighing, a faint sobbing rustle, a little stealthy creak--as though many persons were at his side, holding themselves quite still, and governing even their respiration with the extreme of slyness. The idea went to his vitals with a shock, and he faced about suddenly as if to defend his life. Then, for the first time, he became aware of a light about the level of his eyes, and at some distance in the interior of the house--a vertical thread of light, widening towards the bottom, such as might escape between two wings of arras over a doorway. To see anything was a relief to Denis; it was like a piece of solid ground to a man labouring in a morass; his mind seized upon it with avidity; and he stood staring at it and trying to piece together some logical conception of his surroundings. Plainly there was a flight of steps ascending from his own level to that of this illuminated doorway; and indeed he thought he could make out another thread of light, as fine as a needle, and as faint as phosphorescence, which might very well be reflected along the polished wood of a handrail. Since he had begun to suspect that he was not alone, his heart had continued to beat with smothering violence, and an intolerable desire for action of any sort had possessed itself of his spirit. He was in deadly peril, he believed. What could be more natural than to mount the staircase, lift the curtain, and confront his difficulty at once? At least he would be dealing with something tangible; at least he would be no longer in the dark. He stepped slowly forward with outstretched hands, until his foot struck the bottom step; then he rapidly scaled the stairs, stood for a moment to compose his expression, lifted the arras, and went in.