As soon as we had completed our reconnaissance, we need only walk back in a straight line until the Old Light shone straight in our faces. Then we should turn right at forty-five degrees and make our way steadily towards its iron ladder, along the raised path of the river bank. Or so it seemed. I could already feel the sand yielding more easily underfoot, as the tide seeped beneath us. By the yellow oil-light of my lantern, I could also see that each of my footprints now flooded progressively deeper and more quickly as my boot was lifted from the mud.
Holmes was at his most dogmatic.
“I think we need another half mile to reach the scene of their encounter. I should like to determine a direct line from St Clement’s beacon to the incoming surf.”
As he said this, I noticed that the blurred but luminous line of surf was now the only thing visible to our right between the darkness of sky and sea. We walked for about fifteen minutes more, scarcely exchanging a word. I felt the coldness of the October night coming in with the mist. Even the lemon afterglow of sunset had vanished from the inland horizon beyond the village. The rest of the shoreline was obscure and the descending mist which the rector had described now hung between us and St Clement’s beacon, condensing slowly into fog. I tried a cheerful note.
“The ground seems a little higher here, Holmes, a rib of firm sand. If we follow it back, when we turn, and keep Mr Gilmore’s beacon in view to the right, we should soon have the beam of the Old Light full in our faces.”
“I daresay,” he said impatiently but with no sign of turning back, “If I had been the survivor of that fight between the two brothers on Sunday night, I should have assumed much the same.”
“I thought we had agreed that there was no survivor of the encounter.”
“On the contrary. That is a matter which we are about to put to the proof.”
By this time, I had very little wish to put it to the proof. Indeed, with the light gone, I began not to like the whole business. We were not more than eight feet apart but it had become increasingly difficult to make out the gaunt purposeful stride of my companion or anything but the hazy flicker of his lamp. As if reading my thoughts, he added,
“We must keep together. It may be firm going here but it would be well not to get separated where the sands are more perilous.”
So we walked on until we were, at the very least, level with the beacon of the church tower. It seemed far away now across the flooding sands.
“We must take care that the tide does not get behind us,” I said a little breathlessly.
Holmes was not listening.
“Now stop a bit,” he said, “Let us have our bearings. We are the Chastelnau brothers. Here it is that either you or I kill the other. The killer may have carried out a long-prepared plan. Alternatively, it may have been provocation, a sudden heat and a terrifying accident. In either event, what would the survivor do next?”
“Get back to the Old Light! Where else should he go?”
“Very well, Watson. You have committed murder or, at the least manslaughter. Now, pray lead on.”
This was not what I had bargained for but I was relieved to be turning back before the flood tide encroached any further. As a soldier, I was not unprepared for the challenge. There was no light along the western horizon nor a moon in the sky. The lamps of the village were scarcely pinpricks. I heard an insistent murmuring from the dark billowing sea which was a good deal louder now than when we had set out. For the first time, I noticed a sharp north-east wind gathering at our backs, a light spot or two of cold rain. It was a reminder that, despite the pleasant sunlight of that afternoon, this was the season of equinoctial storms.
When I had joined the Army Medical Department a decade earlier and sailed for Afghanistan with the Northumberland Fusiliers, even a surgeon’s training for service overseas included a course of instruction in map-reading, compass-bearings, judging distances and identifying terrain. In my mind I now constructed a square map. In the top right-hand corner was the beacon of the church tower. In the top left-hand corner was the Old Light. Along the bottom was the line of the incoming tide. Holmes and I were in the bottom right-hand corner, walking parallel with the foot of the map.
We were following what I had judged to be a rib of sand six inches or more above the level of the dark beach around us and therefore firmer. The temptation was to cut a diagonal across the square map towards the Old Light. Fortunately, I had surveyed the terrain from the windows of the barrack-room that afternoon and had seen that such a diagonal would take us into lower ground, probably already flooded by the tide and possibly containing quicksand. The prudent line of march was still to follow the bottom line of the map until we were face-to-face with the lighthouse beam. Then we should know that we had reached the bottom left-hand corner and need only take a right-angle and walk straight into the beam to reach the safety of the iron ladder to the barrack-room.
The sand beneath our feet was softer but there was no doubt that we were still on slightly higher ground. I thought of Holmes’s question and my answer. Suppose I were my brother’s murderer, making my escape. In the first place, it was impossible that I should go anywhere but the Old Light. I assumed that I would not have intended murder when I set out. Therefore I would not have been prepared for immediate flight without returning to the barrack-room.
Holmes said nothing in all this time but appeared content to follow where I led. The light of St Clement’s beacon was dropping away behind us on our right. The beam from the Old Light was ahead but shining at an angle, slightly away from us. We seemed in danger of pulling inland behind it. That must be avoided at all costs for it was where I had noticed earlier that the mudflats lay and the treacherous “shivering sands” might be. It was easy enough to set a course a little further to our left. This brought us slightly closer to the tide but also took us further round on an angle that should put us in the lighthouse beam. Once there, we were safe.
I had begun to feel that a man could make too much of such difficulties as this beach had presented. Then I put my right foot forward and, before I could pull back, felt the leg sink half way up the shin in freezing mud.
“Stop! Stop, Holmes!”
We were almost level with the lighthouse beam but were somehow in the very terrain I had tried to avoid. To one side, among what was now fathomless mud rather than firm sand, I could see strands of grass, limp and wet. Fresh water could mean only the river, which we should not have encountered at all. Though we were still short of the lighthouse beam where it crossed our path, we had somehow come too far. How could that be? How could we be where we evidently were-and how had we got there? The doomed baggage-train of King John, all those centuries ago, had thought themselves secure. Had we made an error in common with them? I had dipped into the chronicles which Holmes had brought and now recalled with dismay a warning that the first step to destruction in shifting sands and estuaries is when the victims lose their way-as we had done now. The ground opened in the midst of the waters, wrote the medieval chronicler Roger of Wendover, and whirlpools sucked down men and horses. It was already too late. To those who might help us, our cries would be inaudible.
The true terror, in the darkness and the fast sinking mud, is to know that one has followed meticulously the path to safety but come only to the verge of a cold and cruel death. There was no explanation and, without that, we were done for. We must move instantly or the incoming tide would overwhelm us-but where was our path? There was nothing but the surf and the sinking sand around us, on every side.