The man made some reply in a language which neither of them understood.

Renstoke repeated his question.

Turning to a telephone which stood on a small table in the lodge the man spoke a few words. A moment later he signed to them to enter and conducted them to the entrance door of the big house.

As they approached a big, powerfully built man, heavily bearded and wearing round horn spectacles, met them on the steps of the front door.

Renstoke bowed courteously. "Mr Erckmann?" he inquired.

"Yes, I am Mr Erckmann," was the reply. "What can I do for you?"

Renstoke as briefly as possible explained what had happened. Erckmann listened patiently and carefully. Only at the end of the story, when Renstoke told him quite frankly his suspicions, the man's eyes hardened ominously and his lips tightened under his heavy grey moustache.

"Yes, I have a gorilla," he admitted. "But if you suggest that it has escaped you are quite wrong. It has never left its cage since it was brought here, quite young, six years ago. It would be a bad thing for some one if it did," he added.

"May we see it?" asked Renstoke quietly.

"Yes--if you doubt my word," snapped the scientist. He was evidently, for some reason, much annoyed and was controlling himself with obvious difficulty.

During the conversation d.i.c.k had once or twice glanced at Yvette and was surprised at the fixity of the gaze she directed at Erckmann. She was regarding him almost as if fascinated, with every sign of horror and apprehension.

Without further words Erckmann led the way through a small paddock to a row of cages, heavily barred with iron, which stood at the rear of the house. Before one of the strongest he halted.

"There you are," he said grimly.

Inside the cage, erect on its hind legs, stood an enormous ape, shackled by a huge chain round its neck to a heavy stake driven into the ground.

Nearly seven feet high, it was so horribly repulsive in its perverted likeness to humanity, that Yvette, d.i.c.k, and Jules turned away sick with disgust and horror. It snarled and chattered at the sight of the strangers.

Renstoke, however, carefully examined the monster. But he soon realised that this creature had certainly not been at large, at any rate for some considerable time.

The clue had failed. Whatever the truth might be it was clear the gorilla could have had no part in the terrible tragedy of Alan MacPherson.

"A wonderful specimen," said Renstoke, turning to Erckmann. "Have you had him long?"

"About six years," the scientist replied. "Would you like to see what it can do?" Without waiting for a reply, he spoke softly to the raging beast in some language the others did not understand.

Instantly the brute calmed down, shuffled to the bars of the cage and laid its head on the ground close to where Erckmann was standing. It was just as though a dog were fawning on its master. Erckmann fearlessly thrust a hand between the bars and scratched the repulsive head while the great ape lay with closed eyes evidently in keen enjoyment of the sensation.

Still talking quietly in the strange language, Erckmann put the beast through a number of tricks which it performed, clumsily, of course, but with obvious understanding of what was required of it. It was, as Renstoke realised, a wonderful example of animal training, for the gorilla is perhaps the most intractable of all living animals.

"Perhaps as you are here you would like to see the rest of my menagerie," said Erckmann, as he led the way to a series of cages adjoining.

They gazed in astonishment at what they saw. There was a superb tiger, several leopards of different species, and at least a dozen wolves. The animals were all clean and well cared for and it was obvious at a glance that none of them could have been wandering for an indefinite period about the country.

"I hope you are satisfied, Lord Renstoke," said Erckmann at last, "that none of my pets is responsible for what has happened?"

"Quite," replied Renstoke. "And I am sorry we had to trouble you. But I am sure you will understand why I came. The affair is so mysterious that I could not leave any possibility unexplored." Erckmann had puzzled them all. The man was perfectly courteous and apparently quite open in his replies to their questions. None the less all sensed that he was ill at ease and that he quite certainly resented their intrusion.

Yvette, more sensitive and keenly strung than the others, shuddered violently as they left the house.

"That man is bad, all bad," she declared vehemently. "He has the eyes of the snake." She had put into words what all had felt, yet had been half ashamed to confess. There was something repulsively snake-like in the steady glare of Erckmann's eyes behind the thick round gla.s.ses.

"I confess I feel like Yvette," said d.i.c.k, "the man gave me the creeps."

Renstoke looked grave.

"He didn't strike me as being quite aboveboard," he admitted. "At the same time, I don't see what he has to conceal. All the cages were occupied and it is certain none of the animals had been loose recently, and if one had broken out there is no reason why he should not say so.

But he may have another ape which he has not shown us?"

They walked a few hundred yards in silence until they had got to the bottom of the hill and approached the little burn that ran down the valley. There was no path, and as chance would have it, they deviated a few yards from the way along which they had come. They were crossing the brook when Yvette gave a slight exclamation.

"Oh, look here," she said.

The bed of the burn was stony throughout, but at one point, at the very edge of the water was a tiny patch of sand, smooth and firm and hardly larger than a handkerchief. Yvette pointed to it.

There, sharply and clearly defined, was the unmistakable imprint of a naked, misshapen foot! It was human beyond all question. It pointed in the direction of the house they had just left, and it was dear that the barefooted walker, whoever he may have been, had stepped from the heather just on to the patch of firm sand and been carried by his next stride through and beyond the rivulet on to the heather and stones where no footprints would remain. By some strange chance that one tell-tale footprint had been left in perhaps the only square foot of ground for miles where an impression could be left!

They examined the footprint with eager curiosity. Evidently the walker, or rather runner, had come fast down the hill, for the front part of the foot was driven deeply into the sand while the heel was only just showing.

"He must have been running," said Renstoke, "and what kind of man could run over such a country as this?"

The question was natural, for the heather grew thick and deep round there and they had found walking difficult enough; running would have been out of the question for any of them.

They were puzzled by the strange footprint, but how little they guessed that it held the key to the terrible tragedy of Renstoke!

Late that night, Renstoke, d.i.c.k, and Jules sat yarning in the great old drawing-room at the Castle. The night was close and sultry, with a threat of thunder in the air, and the big French windows which opened on to the spreading lawn were flung wide.

They were discussing Erckmann.

"I didn't like him," said Renstoke, "though it is recognised that he possesses genius in a marked degree."

"Oh! You've heard something then?" asked d.i.c.k quickly.

"Yes. The general public know nothing of him, but I hear that he has an amazing theory that it is possible, by an operation on the brain, to abolish almost entirely the ordinary characteristics of a man or an animal, and by the injection of an appropriate serum to subst.i.tute the mental, and to some extent the physical, characteristics of another species. He believes that you can, for instance, take a puppy-dog, operate on its brain, inject a serum prepared in some way from the brain of a monkey, and the puppy will grow up with the mentality and habits of a monkey and with its bodily characteristics so transformed that it can do many things--such, for instance, as climb a tree--which no dog could do. I believe he has actually succeeded in doing this!"

"How weird and extraordinary!" remarked Yvette.

"More than this, he believes you could do the same with a human being-- destroy its human attributes and give it, for example, the ferocity, and something of the speed, of a wolf or a tiger."

"How on earth did you learn this, Renstoke?" asked d.i.c.k.

"From perhaps the only person who ever knew Erckmann really well," was the reply. "Some years ago Erckmann was the resident doctor at a lunatic asylum in Prague. He made a particular crony of his chief a.s.sistant, a young doctor named Chatry, who afterwards went to Canada, where I met him. Chatry told me something of Erckmann's views and experiments. I was, of course, tremendously interested, but I little thought I should ever run against the man in the flesh. Erckmann was undoubtedly a very able man, but there was a scandal. On some pretext or other he performed a remarkable operation on an insane person. The patient, who had previously been quite tractable, developed extraordinary characteristics. He growled and snapped at all who approached him, insisted on eating his food on the floor instead of at table, barked like a dog, and finally would only sleep curled up on a rug. In fact, he developed strikingly dog-like habits. How much of anything Erckmann let out generally Chatry never knew. But he was asked to resign, and he left Prague."

"A very curious story!" d.i.c.k remarked.

"Now Chatry had no doubt whatever on the subject," said his host.

"Amazing as it may seem, he was firmly convinced that Erckmann had deliberately made this extraordinary experiment and that it had succeeded. Chatry died just before I left Canada, but before he died, he gave me a little ma.n.u.script book in which he has related the whole story. I'll show it to you to-morrow."

They said good-night and went to bed, leaving Renstoke, who sometimes suffered from insomnia, to read himself sleepy.