The invitation was accepted at once, and in another half minute Cleek and Mr. Narkom found themselves standing in a wonderful white-and-gold room, under a huge crystal chandelier of silver and cut glass, and looking out through an arched opening, hung with sulphur-coloured draperies, into a sort of baronial hall equipped with armour and tapestries, and broad enough to drive a coach through without danger to its contents.

From this hall, as they discovered, when Lady Leake led them without delay toward the scene of the necklace’s mysterious vanishment, a broad, short flight of richly carpeted stairs led to a square landing, and thence another and a longer flight, striking off at right angles, communicated with the passage upon which her ladyship’s boudoir opened.

“It was here that I stood, Mr. Cleek, when I recollected about the necklace as I called Jennifer to me,” she explained, pausing on the landing at the foot of this latter flight of stairs just long enough to let him note, over the broad rail of the banister, that the great hall was clearly visible below. “He was there, just under you, drying the globes of the music-room chandelier when I called to him. Now come this way, please, and you will see how impossible it is for any one to have entered and left the boudoir during my brief absence without my seeing or hearing.”

It was; for the door of the boudoir, which was entirely detached from the rest of the suite occupied by herself and her husband, was immediately opposite the head of the staircase and clearly visible from the landing at its foot.

She unlocked this one solitary door, and let them see that the only other means of possibly entering the room was by way of a large overhanging bay window overlooking the grounds. But this was a good twenty feet above the surface of the earth and there was not a vine nor a tree within yards and yards of it, and as the space beneath was so large and clear that no one could have manipulated a ladder without the certainty of discovery, Cleek saw at a glance that the window might be dismissed at once as a possible point of entry.

Nor did anything else about the room offer a hint more promising. All that he saw was just what one might have expected to see in such a place under such circumstances as these.

On the dressing-table, surrounded by a litter of silver and cut-glass toilet articles, lay the case which had once contained the famous necklace, wide open and empty. Over the back of a chair—as if it had been thrown there under the stress of haste and great excitement—hung a negligée of flowered white silk trimmed with cascades of rich lace, and across a sofa at the far end of the room, a dinner gown of gray satin was carefully spread out, with a pair of gray silk stockings and gray satin slippers lying beside it.

“Everything is exactly as it was, Mr. Cleek, at the time the necklace disappeared,” explained her ladyship, noting the manner in which his glances went flickering about the room, skimming the surface of all things but settling on none. “Everything, that is, but that negligée there.”

“Wasn’t that in the room, then?”

“Oh, yes, but it wasn’t on the chair; it was on me. I had come up to dress for dinner a short time before Henry made his appearance—indeed, I had only just taken off my street costume and started to dress when he rapped at the door and implored me to let him come in and speak to me for a minute or two. ‘For God’s sake, mater!’ was the way he put it, and as haste seemed to be of vital importance, I slipped on my negligée and let him in as quickly as I could. Afterward, when Sir Mawson came in with the wonderful necklace——”