I can do my best...”
I experienced some difficulty in assisting at what followed; but Nayland Smith, his course set, made the injection as coolly as though he had been used to such work for half a lifetime. When it was done:
“If Petrie survives,” he said quietly, “his own skill will have saved him—not ours. Lay that rug over him. It strikes one as chilly in here.”
The man’s self-mastery was almost superhuman.
He crossed to close the windows—to hide his face from me. Even that iron control had its breaking point. And suddenly the dead silence which fell with the shutting of the windows was broken by the buzzing of an insect.
I couldn’t see the thing, which evidently Sir Denis had disturbed, but it was flying about the place with feverish activity. Something else seemed to have arrested Sir Denis’s attention: he was staring down at the table.
“H’m!” he muttered. “Very queer!”
Then the noise of the busy insect evidently reached his ears. He turned in a flash and his expression was remarkable.
“What’s that, Sterling?” he snapped. “Do you hear it?”
“Clearly. There’s a gadfly buzzing about.”
“Gadfly—nothing! I have recently spent many hours in the laboratory of the School of Tropical Medicine. That’s why I’m here! Listen. Did you ever hear a gadfly that made that noise?”
His manner was so strange that it chilled me. I stood still, listening. And presently, in the sound made by that invisible, restless insect, I detected a difference. It emitted a queer sawing note. I stared across at Nayland Smith.
“You’ve been to Uganda,” he said. “Did you never hear it?”
At which moment, and before I had time to reply, I caught a glimpse of the fly which caused this peculiar sound. It was smaller than I had supposed. Narrowly missing the speaker’s head, it swooped down onto the table behind him, and settled upon something which lay there—something which had already attracted Sir Denis’s attention.
“Don’t move,” I whispered. “It’s just behind you.”
“Get it,” he replied, in an equally low voice. “A book, a roll of paper—anything; but for God’s sake don’t miss it...”
I took up a copy of the Gazette de Monte Carlo. One of poor Petrie’s hobbies was a roulette system which he had never succeeded in perfecting. I rolled it and stepped quietly forward.
Nayland Smith stood quite still. Beside him, my improvised swatter raised, I saw the insect distinctly. It had long, narrow, brownish wings and a curiously hairy head. In the very moment that I dashed the roll of paper down, I recognized the object upon which it had settled.
It was a spray of that purple-leaved drosophyllum , identical except that it was freshly cut, with a fragment which I knew to be sealed in a tube somewhere in Petrie’s collection!
“Make sure,” said Sir Denis, turning.
I repeated the blow. Behind us, on the couch, Petrie lay motionless. Sir Denis bent over the dead insect.
“Don’t you know what this is, Sterling?” he demanded.
“No. Flies are a bit outside my province. But I can tell you something about the purple leaves.”
Taking the roll of paper from me, he moved the dead fly further forward upon the polished table-top where direct light fell upon it; then:
“Hullo!” he exclaimed.
He snatched up a lens which lay near by and bent over the insect, peering down absorbedly.
I turned and looked towards the couch were Petrie lay, and I studied his haggard features. I could detect no evidence of life. The purple shadow showed like a bruise on his forehead; but I thought that it had not increased.
Yet I believed he was doomed, already dying, and my thoughts jumped feverishly to that strange plant upon the table—and from the plant to the yellow face which so recently had leered at me out of the darkness.
Was it conceivable—could it be—that some human agency directed this pestilence?
I turned, looking beyond the bent, motionless figure of Nayland