Saluting each of the three in turn, the tall Egyptian passed from Dr. Cairn's room. Upon his exit followed a brief but electric silence. Dr. Cairn's face was very stern and Sime, with his hands locked behind him, stood staring out of the window into the palmy garden of the hotel. Robert Cairn looked from one to the other excitedly.  
"What did he say, sir?" he cried, addressing his father. "It had something to do with—"
 
Dr. Cairn turned. Sime did not move.
 
"It had something to do with the matter which has brought me to Cairo," replied the former—"yes."
 
"You see," said Robert, "my knowledge of Arabic is nil—"
 
Sime turned in his heavy fashion, and directed a dull gaze upon the last speaker.
 
"Ali Mohammed," he explained slowly, "who has just left, had come down from the Fayûm to report a singular matter. He was unaware of its real importance, but it was sufficiently unusual to disturb him, and Ali Mohammed es-Suefi is not easily disturbed."
 
Dr. Cairn dropped into an armchair, nodding towards Sime.
 
"Tell him all that we have heard," he said. "We stand together in this affair."
 
"Well," continued Sime, in his deliberate fashion, "when we struck our camp beside the Pyramid of Méydûm, Ali Mohammed remained behind with a gang of workmen to finish off some comparatively unimportant work. He is an unemotional person. Fear is alien to his composition; it has no meaning for him. But last night something occurred at the camp—or what
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remained of the camp—which seems to have shaken even Ali Mohammed's iron nerve."
 
Robert Cairn nodded, watching the speaker intently.
 
"The entrance to the Méydûm Pyramid—," continued Sime.
 
"One of the entrances," interrupted Dr. Cairn, smiling slightly.
 
"There is only one entrance," said Sime dogmatically.
 
Dr. Cairn waved his hand.
 
"Go ahead," he said. "We can discuss these archæological details later."
 
Sime stared dully, but, without further comment, resumed:
 
"The camp was situated on the slope immediately below the only known entrance to the Méydûm Pyramid; one might say that it lay in the shadow of the building. There are tumuli in the neighbourhood—part of a prehistoric cemetery—and it was work in connection with this which had detained Ali Mohammed in that part of the Fayûm. Last night about ten o'clock he was awakened by an unusual sound, or series of sounds, he reports. He came out of the tent into the moonlight, and looked up at the pyramid. The entrance was a good way above his head, of course, and quite fifty or sixty yards from the point where he was standing, but the moonbeams bathed that side of the building in dazzling light so that he was enabled to see a perfect crowd of bats whirling out of the pyramid."
 
"Bats!" ejaculated Robert Cairn.
 
"Yes. There is a small colony of bats in this pyramid, of course; but the bat does not hunt in bands, and the sight of these bats flying out from the place was one which Ali Mohammed had never witnessed before. Their concerted squeaking was very clearly audible. He could not believe that it was this which had awakened him, and which had awakened the ten or twelve workmen who also slept in the camp, for these were now clustering around him, and all looking up at the side of the pyramid.
 
"Fayûm nights are strangely still. Except for the jackals and the village dogs, and some other sounds
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to which one grows accustomed, there is nothing—absolutely nothing—audible.
 
"In this stillness, then, the flapping of the bat regiment made quite a disturbance overhead. Some of the men were only half awake, but most, of them were badly frightened. And now they began to compare notes, with the result that they determined upon the exact nature of the sound which had aroused them. It seemed almost certain that this had been a dreadful scream—the scream of a woman in the last agony."
 
He paused, looking from Dr. Cairn to his son, with a singular expression upon his habitually immobile face.
 
"Go on," said Robert Cairn.
 
Slowly Sime resumed:
 
"The bats had beg............