PROMPTITUDE was one of Professor Ravenden's many virtues. Only one thing could make him forget the obligation of an engagement; that was his dominant ardour for the hunt. In time this had become an instinct. So it is not strange that, on leaving Third House to keep his rendezvous with Dick Colton, he should have absentmindedly hung his heavy poison-jar for specimens around his neck, and taken up his butterfly net, while entirely forgetting his revolver.

As chance would have it, there rose about the same hour as Professor Ravenden a delicate little butterfly with wings like the azure glory of the mid-June heavens. It was taking the air on a leaf of scrub-oak, while waiting for the sun to come out, when the entomologist came striding over the knolls, and brushed against the shrub. Up fluttered the beautiful insect, and the blue of its wings caught the eager eye of Professor Ravenden. It was of the same species which once before had lured him from the greater pursuit.

“Lycama pseudargiolus,” he muttered, as he hastily affixed his collapsible net. “From its brightness, it should be a fall specimen, and undoubtedly shows the variations on the lower wing which I am studying. Wait one moment, my friend, and I shall welcome you to the hospitality of my cyanide jar.”

After a brief flight the insect settled down well toward the centre of another patch of shrubbery. Having prepared his net, the hunter set about forcing his way into this patch, but before he was in reach of his prey the pressure on the close-knit vegetation had disturbed the sensitive insect and again it rose, this time in alarm. Though barely an inch across the wings, this species exhibits capacities for flight greater than that of much larger butterflies. When again it alighted, the pursuer, panting and perspiring, had been drawn in a semicircular course, some hundreds of yards inland. This time he did not get near enough for a trial of his net before the elusive creature was off again. The third flight was a briefer one. After tentative flutterings, the pseudargiolm alighted on a marshmallow leaf in a hollow. Taking profit of his previous failures, Professor Ravenden sat down and got his breath while waiting for the quarry to lapse into a state of undisturbed quietude. Thus, it was easy presently for the hunter to net it and transfer it to the cyanide jar. This done, he realised with a start of conscience that he had wasted ten minutes, and was a quarter of a mile off the track of his engagement. With all speed, he pointed across the knolls toward the beach.

Fog was drifting in from the ocean, giving added incentive to haste. Wisest it would be, the professor judged, to make for the near point of the cliff, so that he might have a line to follow should mist blot the landscape. The beach below was just dimming with the advance of the first folds of grey when Professor Ravenden reached the brink. The nearer sands were cut off from his vision by a rise between himself and the rendezvous. As his eye ranged to the west for the readiest access to the level, it was caught and held by the outstretched body of Dick Colton lying upon the hard sand out from the mouth of the ravine where Serdholm and Haynes had met their death.

For the moment the scientist was stunned into inaction. Suddenly the body twitched, and there swept over the unhappy entomologist a dreadful sense of his own negligence and responsibility. Along the heights paralleling the beach-line he ran at utmost speed, dipped down into a hollow where, for the time, the prospect was shut off, and surmounted the slope beyond, which brought him almost above the body, and a little to the east of the gully. Meantime the fog had been closing down, and now, as the professor reached the spot, it spread a grey and wavering mantle between him and what lay below.

Already he had attained the gully's edge, when there moved out upon the hard sand a thing so out of all conception, an apparition so monstrous, that the professor's net fell from his hand, and a loud cry burst from him. Through the enveloping medium of the mist, the figure swayed vaguely, and assumed shapes beyond comprehension. Suddenly it doubled on itself, contracted to a compact blur, underwent a swift inversion, and before the scientist's straining vision there arose a man, dreadful of aspect indeed, but still a human being, and as such, not beyond human powers to cope with. The man had been moving toward the body of Colton when the professor's shout arrested him. Now he whirled about and stood facing the height with squinted eyes and bestially gnashing teeth.

To delay him was the one chance for Colton's life, if Colton indeed were not already beyond help.

“If I only could get down the gully!” thought the professor, and dismissed the thought instantly. Time for any course except the direct one now was lacking. The one way lay over the cliff.

“Stand where you are!” he shouted in a voice of command, and before the words were fairly done he was in mid-air, a giddy terror dulling his brain as he plunged down through the fog. Fortunately—for the bones of fifty-odd years are brittle—he landed upon a slope of soft sand. Pitching forward, he threw himself completely over, and carried to his feet by the impetus, charged down the slope upon the man.

It was the juggler. So much the professor realised as he sped forward. Mania of murder was written unmistakably on the seamed and malignant face and in the eyes, as the man turned them on the professor. His posture was that of a startled beast, alert and alarmed. Beyond him, near the sprawled body of Colton, a huge knife with an inordinately broad blade stuck, half upright, in the sand. Toward this the maniac had started, but turned swiftly with a snarl, and crouched, as the intrepid scientist ran in upon him.

Exultation, savage and keen, a most unscientific emotion, blazed up in Professor Ravenden as he noted that his opponent had little the advantage of him in size and weight. What little there was would be offset by his own natural wiriness of frame which a rigid habit of life and out-of-door exercise had kept from the deterioration of age. The scientist came in, stooping low, and, stooping low, the murderer met the onset. The two closed. With a sudden, daunting shock the entomologist realised, as Whalley's muscles tightened on his, that he had met the strength of fury. For a moment they strained, Professor Ravenden striving for a grip which should enable him to break the other's foothold. Then with a rabid scream the creature dashed his face into the professor's shoulder. Through cloth and flesh sheared the ravening teeth, until they grated on the shoulder-blade.

Instantly the aspect of the duel changed. For, upon the outrage of that assault, a fury not less insane than the maniac's fired the professor, and he who always had prided himself upon a considered austerity of the emotions, was roused to the world-old, baresark thirst of murder which lies somewhere, black and terrible, in the soul of every courageous man, and, sends him, at the last, straight to the throat of his enemy.

Power flushed through his veins; his muscles distended with the strength of steel. Driving his fingers deep under the chin, he tore the hideous, distorted face from his shoulder. His right hand, drawn back for a blow, twitched upon the cord from which depended his heavy poison-bottle. Shouting aloud, he swung up the formidable weapon and brought it down upon the juggler's head with repeated blows. The man's grasp relaxed. Back for a fuller swing Professor Ravenden leaped, and crushed him to the ground. The thick glass was shattered, and on the blood-stained sands a little spot of heaven's blue fluttered in the breeze, instantly to be trampled under foot.

Suddenly the scientist swayed and lurched forward. An influence as potent for death as the most murderous weapons of man was abroad, loosed when the glass shattered. The deadly fumes of the cyanide, rising from the base of the jar which its owner still held, were doing their work. With barely sense enough surviving to realise his new peril, he flung it far from him. A mist fell, like a curtain, somewhere between his eyes and his brain, befogging the processes of thought. Heavily he dropped to his hands and knees over the feet of the senseless juggler, his face toward Colton.

Colton seemed to have risen. This the professor took to be a figment of his reeling brain. It annoyed him.

“Lie down! Be quiet!” he muttered. “You are dead, and I am going to kill your murderer!”

Calling up all his will-power, he crawled to the juggler's head and set his fingers to the palpitating throat. Another moment and the death of a fellow-man would have been upon the soul of the scholarly scientist, when an arm under his chest and an insistent voice in his ear brought him back to reason.

“In God's name, Professor, don't strangle the poor devil!”

The baresark grip relaxed. Professor Ravenden collapsed, rolled over on his back and looked up stupidly into the white face of Dick Colton.

“Where—where—is my pseudargiolus?” he asked plaintively.

“It's all right, professor; there wasn't any pseudargiolus. Just lie quiet for a moment.”

Professor Ravenden struggled up to a sitting posture. “Let me rise,” he cried. “I have lost my specimen of pseudargiolus. It fell when the jar broke.”

He looked about him, and his eyes fell on the juggler.

“The pteranodon?” he queried. The mist was clearing from his brain, and his mind swung dizzily back to the great speculation.

“What does it all mean?” he groaned.

“There is the pteranodon!” And Colton laughed shakily as he pointed to the blood-smeared form lying quietly on the sand.

“But those footprints! Those footprints! The fossil marks on the rocks!”

“Footprints on the rock. Handprints here.”

“Handprints?” repeated the professor. “Tell me slowly, I implore you. I must confess to an unaccustomed condition of bewilderment.”

“No wonder. The juggler killed his men by knife-play. He lay hidden in the mouth of the gully, and threw the knife as they came along. After killing them he had to recover his knife. So he walked out upon his hands, leaving the marks which have puzzled us so.”

“But why?”

“He is coming to. We'll ask him.”

In a few minutes “The Wonderful Whalley” was able to sit up and answer questions. All his rage seemed to have gone, and all his cunning. He was cowed and weak and indifferent.

“Why did you kill Serdholm?” asked Colton.

“He beat me,” was the reply.

“And what had you against Mr. Haynes?”

“He sink I was murderer; zat I kill ze sailor.”

“And against me?”

“I see you follow ze trail. I sink you find me.”

“So I probably should. I just had seen the resemblance between my handprint and yours and had jumped forward to examine the next print, when I was struck.”

“Zat jomp safe you,” said the juggler. “Ze butt of ze knife hit as it turn or you would be dead.” He spoke in a matter-of-fact way. While waiting until he should be able to walk, they got a detailed confession from him. He told with perfect frankness of the killing of Serdholm and Haynes and the attack on Colton; but he flatly and rather nonchalantly denied the murder of Petersen the sailor, and the slaying of the sheep.

Coming to the killing of the kite-flier, Colton set a trap for him. “Why did you club him after you had given him the knife?”

“Who?” said the juggler, his eyes growing wide. “Mr. Ely, the man we found dead two nights ago with your knife-wound in his back.”

Whalley displayed a pitiable agitation.

“Ze tall, still man, ze man at ze fisher-house? He ees dead?” he cried.

“You ought to know.”

“I sink he was dead,” said the juggler simply. “I hear zat sound up in ze air.”

Once more he threw his hands upward in that shuddering gesture which had startled them the night of the wreck.

“Zen I hear him cry like a dead man. A great an' terreeble cry! I run to my place an' hide away.”

“He heard the kites,” said Colton to Professor Ravenden. Then to the juggler:

“Now, Whalley, what put it into your head to walk out on your hands after your knife when you killed Mr. Haynes and Serdholm?”

“To make it like ze ozzer tracks,” he replied promptly.

“What other tracks?” cried the two men in a breath.

“Ze tracks of eet I do not know. I see zem; but I do not know. Come, I show you.”

He got unsteadily to his feet, and, guarded on either side, led them down the beach toward the Sand Spit station. After walking about a third of a mile he stopped and cast about him.

“Zere!” he said triumphantly, pointing. Following the instruction, they made out traces of blood and the prints of a lamb's hoof. Leading out to the spot was the dreadful familiar double spoor of talons.

“You did that too,” accused Colton.

For refutation “The Wonderful Whalley” dropped to his knees and laid his hand over one of the marks. The hand more than completely covered the prints.

“You zee?” he said triumphantly.

“Whalley, what made that mark there?” said Professor Ravenden.

Again that strange gesture from the juggler and the quick shuddering in-draw of the shoulders. “Ze death-bird, maybe,” he said.

Nothing more could be gotten from him. They delivered him at the coast-guard station to be turned over to the authorities. When he was out of their hands, Professor Ravenden insisted on returning to look for the remains of his lost specimen, and was relieved at finding one wing intact. Not until he had carefully folded this in paper did he turn to Dick Colton with the question:

“What is your opinion of our problem now?”

“I'm at my wit's end,” said Dick. “Possibly we've got on the trail of another hand-walking knife-thrower.”

“Or the death-bird, the pteranodon,” returned Professor Ravenden quietly.