Billingford's track ran down to Neptune's Seat, where it was lost on the hard surface of the rock. Sir Clinton, without halting, directed his companions' attention to a second trail of male footprints running up towards the rock from the road, and crossed just at the landward side of Neptune's Seat by the traces of Billingford. “There's no return track for these, so far as I can see,” he pointed out, “so it looks as if the murdered man made them.” Without a glance at the body, he stepped up on to the rock, picked up the farther trail of Billingford, and began to follow it as it led along the beach towards Lynden Sands village. The footprints ran along the top of a series of slight whale-backs of sand, behind which lay a flatter zone running up towards the high-tide mark. Nearer the sea, a track showed the inspector's line of advance during the night. After following the trail for nearly a quarter of a mile, Sir Clinton pointed to a change in its character. “This is where he began to run. See how the pace shortens beyond this.” Rather to the surprise of his companions, he continued to follow the trail. “Is it really necessary to go as far as this?” Wendover demanded after a time. “You've come the best part of three-quarters of a mile from the rock. What are you trying to do?” “I'm trying to find out the earliest moment when Billingford could have reached the rock, of course,” sir Clinton explained, with a trace of irritation. A few yards farther on, Billingford's track was neatly interrupted. For twenty feet or so there were no tracks on the sand; then the footprints reappeared, sharply defined as before. At the sight of the gap Sir Clinton's face brightened. “I want something solid here,” he said. “Stakes would be best, but we haven't any. A couple of cairns will have to do. Bring the biggest stones you can lift; there are lots up yonder above the tide-mark.” He set them an example, and soon they had collected a fair number of heavy stones. Sir Clinton, with an anxious eye on the tide, built up a strong cairn alongside the last of Billingford's footprints which was visible. “Now the same thing on the other side of the gap,” the chief constable directed. Wendover suppressed his curiosity until the work in hand was over; but as soon as the second cairn had been erected at the point where Billingford's footprints reappeared on the sand he demanded an explanation. “I'm trying to estimate when Billingford passed that point last night,” Sir Clinton answered. “No, I haven't time to explain all about it just now, squire. We're too busy. Ask me again in twelve hours or so, and I'll tell you the answer to the sum. It may be of importance or it mayn't; I don't know yet.” He turned and glanced at the rising tide.