"Sometimes," said the professor, gently. "And Goya said:

"'_It has come to my ears while in the lands of the Syachas that the Sphyx surely lives, as bolder and more curious men than I may, G.o.d willing, prove to the world hereafter_.'"

"But what is the Sphyx?" I insisted.

"For centuries wise men and savants have asked each other that question. I have answered it for myself; I am now to prove it, I trust."

His face darkened, and again and again he stroked his heavy brow.

"If anything occurs," he said, taking my hand in his left and Miss Barrison's hand in his right, "promise me to obey my wishes. Will you?"

"Yes," we said, together.

"If I lose my life, or--or disappear, promise me on your honor to get to the electric launch as soon as possible and make all speed northward, placing my private papers, the reports of Miss Barrison, and your own reports in the hands of the authorities in Bronx Park.

Don't attempt to aid me; don't delay to search for me. Do you promise?"

"Yes," we breathed together.

He looked at us solemnly. "If you fail me, you betray me," he said.

We swore obedience.

"Then let us begin," he said, and he rose and went to the steel cage.

Unlocking the door, he flung it wide and stepped inside, leaving the cage door open.

"The moment a single pie is disturbed," he said to me, "I shall close the steel door from the inside, and you and Miss Barrison will then dump the rosium oxide and the strontium into the tank, clap on the lid, turn the nozzle of the hose on the cage, and spray it thoroughly. Whatever is invisible in the cage will become visible and of a faint rose color. And when the trapped creature becomes visible, hold yourselves ready to aid me as long as I am able to give you orders. After that either all will go well or all will go otherwise, and you must run for the launch." He seated himself in the cage near the open door.

I placed the steel tank near the cage, uncoiled the hose attachment, unscrewed the top, and dumped in the salts of strontium. Miss Barrison unwrapped the bottle of rosium oxide and loosened the cork. We examined this pearl-and-pink powder and shook it up so that it might run out quickly. Then Miss Barrison sat down, and presently became absorbed in a stenographic report of the proceedings up to date.

When Miss Barrison finished her report she handed me the bundle of papers. I stowed them away in my wallet, and we sat down together beside the tank.

Inside the cage Professor Farrago was seated, his spectacled eyes fixed on the row of pies. For a while, although realizing perfectly that our quarry was transparent and invisible, we unconsciously strained our eyes in quest of something stirring in the forest.

"I should think," said I, in a low voice, "that the odor of the pies might draw at least one out of the odd dozen that came rubbing up against my window last night."

"Hush! Listen!" she breathed. But we heard nothing save the snoring of the overfed dog at our feet.

"He'll give us ample notice by b.u.t.ting into Miss Barrison's skirts," I observed. "No need of our watching, professor."

The professor nodded. Presently he removed his spectacles and lay back against the bars, closing his eyes.

At first the forest silence seemed cheerful there in the flecked sunlight. The spotted wood-gnats gyrated merrily, chased by dragon-flies; the shy wood-birds hopped from branch to twig, peering at us in friendly inquiry; a lithe, gray squirrel, plumy tail undulating, rambled serenely around the cage, sniffing at the pastry within.

Suddenly, without apparent reason, the squirrel sprang to a tree-trunk, hung a moment on the bark, quivering all over, then dashed away into the jungle.

"Why did he act like that?" whispered Miss Barrison. And, after a moment: "How still it is! Where have the birds gone?"

In the ominous silence the dog began to whimper in his sleep and his hind legs kicked convulsively.

"He's dreaming--" I began.

The words were almost driven down my throat by the dog, who, without a yelp of warning, hurled himself at Miss Barrison and alighted on my chest, fore paws around my neck.

I cast him scornfully from me, but he scrambled back, digging like a mole to get under us.

"The transparent creatures!" whispered Miss Barrison. "Look! See that pie move!"

I sprang to my feet just as the professor, jamming on his spectacles, leaned forward and slammed the cage door.

"I've got one!" he shouted, frantically. "There's one in the cage!

Turn on that hose!"

"Wait a second," said Miss Barrison, calmly, uncorking the bottle and pouring a pearly stream of rosium oxide into the tank. "Quick! It's fizzing! Screw on the top!"

In a second I had screwed the top fast, seized the hose, and directed a hissing cloud of vapor through the cage bars.

For a moment nothing was heard save the whistling rush of the perfumed spray escaping; a delicious odor of roses filled the air. Then, slowly, there in the sunshine, a misty something grew in the cage--a glistening, pearl-tinted phantom, imperceptibly taking shape in s.p.a.ce--vague at first as a shred of lake vapor, then lengthening, rounding into flowing form, clearer, clearer.

"The Sphyx!" gasped the professor. "In the name of Heaven, play that hose!"

As he spoke the treacherous hose burst. A showery pillar of rose-colored vapor enveloped everything. Through the thickening fog for one brief instant a human form appeared like magic--a woman's form, flawless, exquisite as a statue, pure as marble. Then the swimming vapor buried it, cage, pies, and all.

We ran frantically around, the cage in the obscurity, appealing for instructions and feeling for the bars. Once the professor's m.u.f.fled voice was heard demanding the wearing apparel, and I groped about and found it and stuffed it through the bars of the cage.

"Do you need help?" I shouted. There was no response. Staring around through the thickening vapor of rosium rolling in clouds from the overturned tank, I heard Miss Barrison's voice calling:

"I can't move! A transparent lady is holding me!"

Blindly I rushed about, arms outstretched, and the next moment struck the door of the cage so hard that the impact almost knocked me senseless. Clutching it to steady myself, it suddenly flew open. A rush of partly visible creatures pa.s.sed me like a burst of pink flames, and in the midst, borne swiftly away on the crest of the outrush, the professor pa.s.sed like a bolt shot from a catapult; and his last cry came wafted back to me from the forest as I swayed there, drunk with the stupefying perfume: "Don't worry! I'm all right!"

I staggered out into the clearer air towards a figure seen dimly through swirling vapor.

"Are you hurt?" I stammered, clasping Miss Barrison in my arms.

"No--oh no," she said, wringing her hands. "But the professor! I saw him! I could not scream; I could not move! _They_ had him!"

"I saw him too," I groaned. "There was not one trace of terror on his face. He was actually smiling."

Overcome at the sublime courage of the man, we wept in each other's arms.

True to our promise to Professor Farrago, we made the best of our way northward; and it was not a difficult journey by any means, the voyage in the launch across Okeechobee being perfectly simple and the trail to the nearest railroad station but a few easy miles from the landing-place.

Shocking as had been our experience, dreadful as was the calamity which had not only robbed me of a life-long friend, but had also bereaved the entire scientific world, I could not seem to feel that desperate and hopeless grief which the natural decease of a close friend might warrant. No; there remained a vague expectancy which so dominated my sorrow that at moments I became hopeful--nay, sanguine, that I should one day again behold my beloved superior in the flesh.

There was something so happy in his last smile, something so artlessly pleased, that I was certain no fear of impending dissolution worried him as he disappeared into the uncharted depth of the unknown Everglades.

I think Miss Barrison agreed with me, too. She appeared to be more or less dazed, which was, of course, quite natural; and during our return voyage across Okeechobee and through the lagoons and forests beyond she was very silent.