a great part of the space before it, and there was a working bench in a corner opposite the door. In racks were rows of test tubes, each bearing a neatly written label, and there were files of specimen slides near the big microscope.
I noted the new pane of glass in a section of window which had been cut out one night less than a month ago when some strange burglar had broken in and explored the place. Since that time Petrie had had steel shop-blinds fitted to the interior of the windows, which could be closed and locked at night.
He had never secured any clue to the identity of the intruder or formed any reasonable theory as to what his object could have been.
At that moment, several of the windows were open, and sunlight streamed into the place. There was a constant humming of bees in the garden outside. Petrie took up a little sealed tube, removed the stopper, and shook out the contents of the tube into a glass tray. He turned to me, a strange expression upon his haggard brown face.
“Can you identify this, Sterling?” he asked. “It’s more in your line than in mine.”
I found it to consist of several bruised leaves, originally reddish purple in colour, attached to long stalks. I took up a lens and examined them carefully, the doctor watching me in silence. I saw, now, that there were pollen-like fragments adhering to a sticky substance exuded by the leaves.
There were some curious brown blotches, too, which at first I took to be part of the colouring, but which closer examination showed to be due to a stain.
“It’s drosophyllum,” I murmured, “one of the fly-catching varieties, but a tropical species I have not come across before.”
Petrie did not interrupt me, and:
“There are stains of what looks like dark brown mud,” I went on, “and minute shiny fragments of what might be pollen—”
“It isn’t pollen,” Petrie broke in. “It’s bits of the wing and body of some very hairy insect. But what I’m anxious to know, Sterling, is this—”
I put down the lens and turned to the speaker curiously. His expression was grimly serious.
“Should you expect to find that plant in Europe?”
“No, it isn’t a European variety. It could not possibly grow even as far north as this.”
“Good. That point is settled.”
“How do you account for the stains?”
“I don’t know how to account for them,” Petrie replied slowly, “but I have found out what they are.”
“What are they?”
“Blood!—and what’s more, human blood.”
“Human blood!”
I stopped, at a loss for words.
“I can see I am puzzling you, Sterling. Let me try to explain.” Petrie replaced the fragments in the tube and sealed it down tightly.
“It occurred to me this morning,” he went on, “after you had gone, to investigate the spot where our latest patient had been at work. I thought there might be some peculiar local condition there which would give me a new clue. When I arrived, I found it was a piece of steeply terraced kitchen-garden—not unlike our own, here. It ended in a low wall beyond which was a clear drop into the gorge which connects Ste Claire with the sea.
“He had been at work up to sunset last evening about halfway down, near a water tank. He was taken ill during the night, and this morning developed characteristic symptoms.
“I stood there—it was perfectly still; the people to whom the villa is leased are staying in Monte Carlo at present—and I listened for insects. I had gone prepared to capture any that appeared.”
He pointed to an equipment which lay upon a small table.
“I got several healthy mosquitoes, and other odds and ends. (Later examination showed no trace of parasite in any of them.) I was just coming away when, lying in a little trench where the man had apparently been at work up to the time that he knocked off—I happened to notice that.”
He pointed to the tube containing the purple leaves.
“It was bruised and crushed partly into the soil.”
He