"Some years ago Erckmann was the resident doctor at alunatic asylum in Prague. He made a particular crony of his chiefassistant, a young doctor named Chatry, who afterwards went to Canada,where I met him. Chatry told me something of Erckmann's views andexperiments. I was, of course, tremendously interested, but I littlethought I should ever run against the man in the flesh. Erckmann wasundoubtedly a very able man, but there was a scandal. On some pretextor other he performed a remarkable operation on an insane person. Thepatient, who had previously been quite tractable, developedextraordinary characteristics. He growled and snapped at all whoapproached him, insisted on eating his food on the floor instead of attable, barked like a dog, and finally would only sleep curled up on arug. In fact, he developed strikingly dog-like habits. How much ofanything Erckmann let out generally Chatry never knew. But he was askedto resign, and he left Prague."

  "A very curious story!" Dick remarked.

  "Now Chatry had no doubt whatever on the subject," said his host."Amazing as it may seem, he was firmly convinced that Erckmann haddeliberately made this extraordinary experiment and that it hadsucceeded. Chatry died just before I left Canada, but before he died,he gave me a little manuscript book in which he has related the wholestory. I'll show it to you to-morrow."

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

  It was about two o'clock when Dick, who was a light sleeper, was rousedby a shout for help, apparently from the drawing-room which was directlybelow his bedroom. Instantly he sprang out of bed, and snatching up arevolver, rushed downstairs.

  But he was just too late.

  As he entered the brilliantly lighted drawing-room he caught sightthrough the open window of a heavy misshapen body disappearing into thegloom beyond the bright patch of light cast by the electric lamps on thelawn outside.

  Renstoke lay on his back on the floor, dying beside his favourite chair.Close by was the book he had been reading and on the carpet near it washis pipe, the tobacco still smouldering.

  Dick knelt hastily by the side of his friend and sought frantically torevive him. But it was in vain. The young peer died in his arms. Itwas evident that he had been attacked without the slightest warning, andmercilessly strangled.

  And in the side of his throat, just above the jugular vein, was a deepwound, horribly lacerated, from which the blood flowed in a heavystream.

  The Castle was speedily aroused, and in a few minutes half a dozen menwere busily searching the surrounding country. But it was in vain--themysterious assailant of the unfortunate Lord Renstoke had vanishedcompletely.

  The following day Dick, Jules, and Yvette, almost overcome with grief,were discussing the loss of their friend.

  "There is some devilry at work," Dick declared. "And I shall never resttill it is cleared up, if I spend the rest of my life here."

  Yvette burst into a furious philippic against Erckmann. "That man is atthe bottom of it all," she insisted.

  "But, Yvette," Dick remonstrated, "we have no kind of evidence of that."

  "I don't care," she replied vehemently, "Erckmann knows all about it. Ishould like to choke it out of him," she ended viciously in French.

  "Well," said Jules, "we can't go to Lockie and accuse him. How abouttrying a trap of some kind?"

  "We might do it in that way," Dick admitted. "But what kind of trap?"

  Long and eagerly they discussed the matter, and at length a plan wasevolved.

  The next morning brought them a visit from Inspector Buckman, one of theablest men of the Special Branch at Scotland Yard, to whom, utterlybaffled, the police had very wisely applied for help. He was well knownto all of them as a keen, capable man of infinite resource and undauntedcourage.

  Buckman listened closely while Dick ran over the story, putting in akeen question here and there.

  "We have got to keep the real facts quiet," he said at length."Erckmann must not suspect that we have the smallest inkling of theevidence of Lord Renstoke's death. I will fix that up with thecoroner."

  It was an easy matter. Renstoke Castle was a remote spot, and while theaffair, of course, could not be entirely concealed, it was a simplematter to keep the exact details secret. All the public learned wasthat Lord Renstoke had been attacked and murdered presumably by aburglar for whom a close search was being made.

  But behind all and working in secret the keen brains of Dick, Yvette,Jules, and Buckman were busy.

  Two or three nights later the word went round to the scattered farmsthat every single head of stock was to be driven in to the farms andrigidly confined in the buildings from dusk to daybreak. So far as theycould ensure it not a single living thing was at large.

  Dick's trap was arranged on the hill-side a mile from Renstoke.

  Four inches above the ground, in a circle fifty yards in diameter, ran athin electric wire supported at intervals on small insulated posts.Just inside the circle, on the side away from Renstoke, a sheep wastethered to a strong stake. In the centre of the circle from a tallpole hung a powerful magnesium flash, electrically connected so that itwould be at once exploded by any pressure on the encircling wire, andmomentarily light up with day-time brilliance a large patch of thesurrounding country.

  As dusk fell, Dick, Yvette, Jules, and Buckman carefully crossed thewire and took up their positions in the centre of the circle, lying fulllength in the sheltering heather, and each with a revolver ready tohand. In a leash beside Dick lay Spot, his favourite Airedale, whocould be trusted to give warning of the approach of any intruder, andafterwards to track him remorselessly.

  As the leaden moments dragged by it grew darker and darker until thecountry-side was plunged in pitch blackness. The strain on the watcherswas terrific. They could not smoke or talk, they hardly dared to move.

  Hour after hour dragged by. Midnight passed. Dick, half asleep, wasgently stroking the back of the Airedale.

  Suddenly he felt the animal stiffen, and the hair along its backbristled ominously. A moment later the dog gave a low, half-audiblegrowl and rose to its feet. Instantly the party were keenly alert.

  Dick clapped his hand over the dog's muzzle, and the well-trained animalsubsided into silence. But Dick could feel that it was straininglyalert; obviously it sensed an intruder.

  Keenly at attention, with every faculty strained to the utmost, thesilent watchers heard not a sound. But a few moments later there was avicious snap in the air above them as the magnesium flash exploded,turning the inky blackness for a fraction of a second into a blaze ofdazzling light.

  In that brief outburst of radiance the four caught a glimpse of a horrorthat photographed itself indelibly on their memories.

  Twenty-five yards away a bestial, hideous face loomed out in the glareof light. It was the epitome of all things evil, with wild matted hair,staring eyes and a horrible misshapen mouth drawn back in a snarl whichshowed two rows of monstrous teeth. The body they could not see.Apparently the creature was crouching in the heather so that only itsghastly head was visible.

  Had it been a wild animal not one of the four, their nervessteel-hardened by the war, would have felt a tremor. But that ghastlyface, vile and brutal as it was, was unmistakably human, and for aninstant the watchers were paralysed with uncontrollable terror.

  But it was only for a moment.

  Four revolver shots rang out almost simultaneously, fired in thedarkness at the spot where the apparition had appeared. A cracklingvolley followed as the four automatics were emptied. Almost with thelast shot came a howl of mingled rage and pain from the darkness.Evidently a bullet had got home.

  A few moments later Dick, with Spot barking madly and tugging wildly athis leash, had plunged into the blackness in hot pursuit at the fiendishintruder. Close behind him came Yvette, Jules, and Buckman.

  The hunt had begun!

  Of that wild dash across country in the darkness Dick afterwardsremembered but little. Spot plunged ahead without hesitation and D
ickfollowed, intent only on making the best speed possible and careless ofconstant falls as he stumbled blindly along. He dared not loose thedog, for without it he would have been helpless, and he plunged blindlyforward, his reloaded pistol grasped in his right hand, careless ofhimself and intent only on overtaking the horror which he knew laysomewhere ahead of him. Behind him toiled the others, guided by Spot'sfrantic barks.

  Progress, of course, was slow; falls and stumbles every few momentschecked the pace; the darkness was baffling. It was with feelings ofintense relief that Dick at length saw the silvery edge of the moonlifting itself above the hills behind him. He had lost all sense ofdirection, but the moon rising behind him told him he was travellingwestward.

  Half an hour later the country was bathed in soft light and Dick wasable to pick up his bearings. Suddenly he realised with a shock that hewas heading straight for Lockie!

  Dick halted to let the others