As the Professor strode on through the silence, devoid of any vestige of human habitation, he noticed how admirably adapted was this barren heath to purposes of concealment. Spread over its surface were a series of shallow depressions, shaped like a saucer, and sometimes holding an abandoned gravel pit, now half filled with stagnant water after the winter rains. A man might lie concealed in one of these, secure from observation, for as long as he could keep himself supplied with food. There would be no risk of discovery, those whose business led them to cross the heath kept strictly to the narrow paths, barely a foot wide, which meandered at wide intervals through the close growth of heather. A living man, so long as he avoided observation from these paths, might lie hidden for as long as he chose. And if a living man, why not a dead body? How easy to drag the damning evidence of crime into one of those dark thickets, to sink it into the silent depths of one of those black, unruffled pools! The Professor shuddered, and increased his pace. This lonely heath was no place in which to indulge in morbid thoughts. His life might be in danger, but somehow he felt that it was not here that the blow would fall. If his theory were correct, if he had gauged aright the psychology of his adversary, it would not be thus that he would meet his death, here where there was none to witness the blow. Despite the almost threatening aspect of the country, deepening in tone every instant as the sun sank lower behind the distant hills, there was no vestige of any real danger. The shadows that lurked amid the gorse and heather were but the shadows of his own fears. 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.