So the Professor reasoned with himself. It would have been folly for him, wishing as he did to avoid any suspicion of his interest in Dr. Morlandson, to approach the scene of his death during the day. The very track by the side of which he was walking contained a potential risk of discovery. It must be used sometimes, the rails showed signs that wagons had passed over them not so very long ago. They led only to a pier, or rather jetty, upon which the contents of the wagons were unloaded into a waiting barge. The pier was utterly unfrequented except by these barges. The track, in fact, was a dead end as far as any casual wayfarer was concerned. There could be no rational excuse for following it.
He topped a slight rise, and saw in the distance the white surface of the clay-pit which was to be his guide. From where he stood, he could see a considerable distance on either side of him. There was no sign of life upon the heath, except that far away, perhaps a couple of miles, the outlines of a cottage stood out against the grey background.
The Professor reached the clay-pit, and searched the undulating surface of the heath for some sign of the remains of Dr. Morlandson’s laboratory. For some moments he failed to find it, and then, at last, he made out the jagged tooth of a broken wall thrust upwards from behind a clump of gorse bushes. This, no doubt, must be his goal. There was no path leading to it from the track, but the Professor, using his stick to feel the way, stepped out boldly across the heather, which yielded like a cushion to his footsteps.
The distance from the track to the ruin must have been six or seven hundred yards. It took the Professor some little time to cover it, since he was obliged to make several detours in order to avoid clumps of gorse. But he reached it at last, and stood on the edge of what had once been a clearing, surveying the scene that lay before him.
The cottage itself had completely vanished. All that remained of it was a mound thickly overgrown with weeds and coarse grass, from which protruded here and there fragments of charred beams and rafters. The encroaching heath had hidden any signs of any garden there might once have been, and it was impossible for the Professor to form any idea of what the place had looked like while it was still standing. But the laboratory, having been built of concrete, had defied the utter obliteration to which the rest of the premises had succumbed. Its broken walls, rough and jagged, stood up in a gaunt rectangle, roofless, their foundations hidden deep in the all-effacing vegetation, but still marking without fear of error the site upon which the building had stood.
The Professor pushed through the weeds and undergrowth until he reached the gap in the wall where the door had been. The door was still there, rusty and twisted, lying almost hidden at the base of the wall, where it had been thrown by Dr. Morlandson’s would-be rescuers. It was a plain sheet of iron, fitted with hinges and a lock. The Professor glanced at it, then passed through the door-way into the space enclosed between the walls. Something, perhaps a grass-snake, rustled among the grasses as he entered.
The laboratory had been a fairly spacious room, about thirty feet by fifteen. Of its interior fittings nothing whatever remained. As the Professor advanced into the interior of the space his boots struck metal at every other step. He stooped and probed with his stick, and brought to light a twisted and shapeless tangle of iron, which might once have been the frame of a skylight. He examined it for a moment, and then cast it aside, with a nod of comprehension. The walls themselves still showed upon their interior surface the signs of having been subjected to an enormous heat. He poked about inside the laboratory for a short while longer, then came out and sat down upon the mound which had once been a cottage.
There could be no doubt that the fire which had destroyed the laboratory had been far fiercer than that which had burnt down the cottage. The charred beams of the latter still existed, while nothing whatever remained of the wooden fittings of the former. And yet, in case of a concrete-built laboratory, one would have expected a fire merely to have burnt out the interior without doing much damage to the structure. The place must certainly have contained a large quantity of substances whose combustion produced great heat, such as thermite. And Dr. Priestley knew enough of the methods of research chemists, who as a rule deal in very small quantities, to wonder why Dr. Morlandson required such large quantities, and why, even supposing that his isolated situation made it necessary for him to obtain his supplies in bulk, he should store them in the laboratory itself. The suspicion that Dr. Morlandson’s activities had not been solely concerned with researches into the properties of medicinal drugs seemed to the Professor to be thoroughly well grounded.
To the Professor’s mind, there was even something suspicious about the origin of the fire itself. Dr. Morlandson had been aware of the danger of such an outbreak; he had warned the police superintendent against smoking in the laboratory. This being so, was it likely that he would lock himself into what had proved to be a regular death-trap, and leave himself with no means of escape? The doubt raised by these queries set the Professor’s mind to work upon an entirely fresh train of thought. Had Dr. Morlandson’s death been as accidental as it had appeared? Or was it possible that he too had had an enemy, who had somehow contrived the whole affair? And, if so, what became of the theory which had brought the Professor to the Isle of Purbeck?
The Professor awoke with a start from his meditations, suddenly conscious that the light was failing rapidly. It was already past sunset, the ruined Castle which was to be his landmark was now indistinguishable against the universal grey of its background. A faint, silvery mist was rising above the heath, wreathing every object within sight with a curious opalescent halo. The Professor realized that he had already spent long enough contemplating this deserted heap of ashes. Their secret, did they hold one, was not to be wrested from them by further study that night.