"For what?" he demanded, in a dull, accentless voice.

"For a totally new species of human being, Grue. I wish to catch one and take it back to New York in that folding cage."

His green eyes had grown narrow as though sun-dazzled. Kemper had stepped behind us into the woods and was now busy setting up the folding cage. Grue remained motionless.

"I am going to offer you," I said, "the sum of one thousand dollars in gold if you can guide us to a spot where we may see this hitherto unknown species—a creature which is apparently a man but which has, in the back of his head, a third eye—"

I paused in amazement: Grue's cheeks had suddenly puffed out and were quivering; and from the corners of his slitted mouth he was emitting a whimpering sound like the noise made by a low-circling pigeon.

"Grue!" I cried. "What's the matter with you?"

"What is he doing?" screamed Grue, quivering from head to foot, but not turning around.

"Who?" I cried.

"The man behind me!"

"Professor Kemper? He's setting up the folding cage—"