[Illustration: A diagram of various sets of footmarks. At the bottom of the diagram is a road, labeled “To Lynden Sands” on the right. Centered at the top of the diagram is an oval shape labeled “Neptune’s Seat,” to which are connected five different sets of tracks. One set, labeled “Billingford,” arrives at Neptune’s Seat from the right, and then continues downwards towards the road. Two other sets lead from the road to Neptune’s Seat and then back again. One is labeled “Woman’s Light Shoes,” and the other is labeled “Woman’s Golf Shoes.” The latter tracks connect with the road at the same points as a set of motorcar tracks. A fourth set of footmarks, labeled “Murdered Man,” leads from the road to Neptune’s Seat but not back. Along the left edge of the diagram is a heavy line labeled “Groyne,” and a fifth set of tracks, labeled “Man’s Shoes,” comes from the road alongside the groyne and then back again.] “We may as well start with this track,” Sir Clinton suggested. “It's a fairly short one, and seems isolated from all the others by the groyne.” He stepped down on to the sand, taking care to keep well away from the footmarks; and his companions followed his track. They walked on a line parallel to the footprints, which ran close under the groyne. At first the marks were hardly defined; but suddenly they grew sharp. “This is where he hit the sand wetted by the tide, obviously,” said Wendover. “But the trail looks a bit curious—not quite like a normal man's walk.” “Suppose he'd been crouching under the groyne as he went along,” Sir Clinton suggested. “Wouldn't that account for it? Look!” He moved on to a piece of untouched sand, bent almost double, and began to move cautiously along. Wendover and the inspector had to admit that his tracks were very like those of the trail beside the groyne. “Somebody spying on the people on the rock?” Wendover hazarded. “If you can get hold of him, Clinton, he ought to be a useful witness.” The inspector stooped over the footprints and scanned them closely. “It's a clear impression. A man's shoe with a pointed toe, it seems to be,” he announced. “Of course, if he was creeping along behind the groyne we can't get his ordinary length of step, so we haven't any notion of his height.” Sir Clinton had moved on to the end of the trail. “He evidently crouched down here for quite a while,” he pointed out. “See the depth of these impressions and the number of times he must have shifted the position of his feet to ease his muscles. Then he turned back again and went back to the road, still crouching.”