“Then our friend Cargill told us his yarn about meeting Derek Fordingbridge in the war; and off he went to meet his dear old friend. And later on he volunteered eagerly that he'd had a talk with the dear old fellow. By that time I was more than a bit suspicious of the dear old friend; and naturally some of that suspicion spilled over on to Cargill. If the claimant was an impostor, then the man who recognised him was a liar; and, as I had no use for aimless liars in a case of this sort, I inferred that Master Cargill was one of the gang, posted at the hotel for intelligence purposes—to keep an eye on the Fordingbridge group. And that cleared up one of the main difficulties I'd had—namely, how the murderer had known to use a .38 automatic so as to match the Fleetwood pistol. Of course, if you assume that Cargill had taken the opportunity of rummaging in Fleetwood's room, or had drawn him into talk about pistols, they would be sure of their ground on that point. That had been a troublesome point to me; for I didn't like to stretch coincidence to the extent of assuming it was mere accident that made the Fleetwood pistol and the bullet in the body both of the same calibre. “It remained to check Billingford's story as far as possible, and you know how the runnel helped us in that. What the facts of the case proved beyond any reasonable doubt was that at 11.19 p.m. Billingford was about three-quarters of a mile from Neptune's Seat. With the sound of the sea in his ears, it's most unlikely that he could hear a pistol-shot at that distance. And his tracks showed him walking along quite steadily there. Then, at a point far nearer the rock—a point that I suppose he may have reached about 11.35 p.m.—the trail showed that he began to run. Now that fitted in with his story. At that second point he might quite well have heard a shot fired on the rock, just as he said he did. He couldn't possibly, on the facts we established, have reached the rock before about 11.37 or 11.38; and by that time the murder was done and the murderer had got away. “By that time I felt fairly sure of my ground; and I got that digging in the sand started, just on the off-chance that we might get hold of the shell of the cartridge which really did kill Staveley. It wasn't absolutely necessary for the case; but, if it turned up, then it would help to confirm my notions. As it was bound to be below tide-mark, there was no point in trying to locate its exact position, since it might have been washed about by the waves in the falling tide after the shot was fired. So I simply had the whole strip of sand dug up and dumped down above the high-water mark for future examination.