The tide reached its full, shortly after two o’clock, and then began to ebb. Almost at once the little waves of the lagoon smoothed out, they lapped no more against the craggy margin, and the water lay like a sheet of gray glass. I had seen the same transformation on several previous occasions, but to-night it seemed to get hold of me as never before.

Seemingly it partook of a miraculous quality to-night—as if winds had been suddenly stilled by a magician’s art. The water was of course flowing out between the crevices of the rock wall, yet there was no sense of motion. The water-line dropped slowly down.

It is an unescapable fact that the whole atmosphere of the Ochakee country is one of death. The moss-draped forests seem without life, the rivers convey no sense of motion, the air is dead, and vegetation rots underfoot. To-night the lagoon was without any image or indication of life. The whole vista seemed like some dead, forgotten wasteland in a dream—a place where living things had never come and was forever incompatible with life.

It was a mysterious hour. The half-crescent moon rose at last, at first a silver tinting of the skyline, a steadily growing wave of light and then the sharply outlined moon itself above the eastern forest. The dark shadows that were my companions took form, strengthened; again I could see their erect figures on the gray crags and the gleam of their rifles in their arms. The perspective widened, the rock wall seemed to extend, stretch ever further across the lagoon, and now the sky was graying in the East.

A moment later I heard Weldon’s voice, ringing full in the hush of the dying night, as he spoke Slatterly’s name. The latter answered at once.

“Yes. What is it?”

“Let’s go in. The night’s over and nothing’s happened. It’s pretty near bright day already.”

It was true that the eastern sky had begun to be tinged with gray. I could see the lines of my hands and the finer mechanisms of the rifle. The hour, however, seemed later than it really was, simply because of the effulgence of the moon. The dread atmosphere of Kastle Krags had in a moment been wholly destroyed. Instead of a place of mystery and peril, it was simply an old-time manor-house fronting the sea, built between the forest and a calm lagoon.

There didn’t seem any use of watching further. If the night was not yet, in fact, completely over, the moon and the graying east gave the effect of morning. Perhaps the fact that the outgoing tide had stilled the lagoon had its effect too. The ominous sound of breaking waves was gone, and it gave a perfect image of quietude and peace.

Slatterly waited an instant before he answered. “Wait a little more,” he said in a resigned tone. “But you’re right—it’s almost morning.”

I don’t think it was five minutes later that I saw Weldon leave his post and saunter over to the sheriff’s side. I suppose, bored with his task, the time seemed much longer to him. True, the lagoon was gray, the shadows of the garden had lost their mystery, and there didn’t seem any use of waiting. Indeed, I don’t think any of us escaped a sense of inner embarrassment—something akin to ignominy and chagrin—that we should be standing beside that quiet water-body, with high-powered rifles in our hands. It made us feel secretly ridiculous.

Nopp called over, cheerily, “Through for the night?”

“Might as well,” Slatterly answered. “It was a fool party anyway.”

Very glad that the watch was over, I left my own post, and we had a cigarette apiece beside the still lagoon. Then we went through the gardens to the house.

“We’ve disrupted the regular schedule, anyway,” Nopp said. “I think we’ve come to the end of our trouble, and nothing more to fear. Man, do you think to-day will clear the thing up?”

“What chance is there to clear up such a mess in one day?” The sheriff spoke moodily.

“Because you’re going to have some real help—not a lot of bungling amateurs. You know who’s coming?”

“Lacone—Van Hope’s detective.”

“Yes. He’s a distinguished man—a real scientist in the study of crime. He may do wonders, even in one day.”

“I only hope he does! I don’t care who clears it up—as long as it’s cleared. Now to get a little sleep.”

Tired out, we went to our rooms. The cool of early morning had swept through the halls, and the first glimmer of dawn was at the windows. How white the moon was in the sky, how mysteriously gray the whole sweep of shore and sea! So tired I dreaded the work of undressing, I sat down a moment before the window that overlooked the lagoon.

The moonlight and the dawn gave the appearance of a mist, a gray mist as is sometimes seen over water when the sky is overcast with heavy clouds. At that moment it was impossible to conceive of anything but grayness. The whole conception that the brain had, the only interpretation that the senses made was of this same, lifeless hue. If an artist had tried to paint the picture that was spread before my window he would have needed but one tube of paint.

It was in some way vaguely startling. It went home to some dark knowledge within a man, and left him fearful and expectant. The shore and the sea were gray, the gardens were swept with grayness, the lagoon itself had lost its many colors and only the same neutral tint remained. The only way that the eye could distinguish shore from sea, and garden from shore, was the gradations of the same hue.

Surely dawn was almost at hand. The moon looked less vivid in the sky. And nothing remained but to find what sleep I could.

But at that instant my senses quickened. I could hardly call it a start—it was just a sudden wakening of mind and body. I wasn’t the least sure.... Perhaps in a moment the old lull, the well-remembered sense of well-being and security would return. It had seemed to me that a swift shadow glided through the grayness at the shore of the lagoon.

The window afforded a remarkably wide glimpse of that particular part of the estate. The rift in the trees permitted a view of scattered segments of the rock wall itself. And it wasn’t to be that I could turn and leave them to the gray of morning. In that mysterious, eerie light I saw the whisking shadow again.

It was not merely some little creeping thing from the forest—some living creature such as stirs about at the first ray of dawn. The shadow was much too large. I would have thought, at the first glance, that it was the shadow of a man. But at that instant the figure emerged into the open, and I knew the truth.

The trim form on the shore of the lagoon was that of Edith Nealman. I could see her outline with entire plainness, dark against the gray. Some errand of stealth had taken her down to the shore of the lagoon the moment that it was left unguarded.

In an instant she disappeared, and in the interval I found out how deeply and inexplicably startled I was. And then I saw her again, walking out on the natural rock bridge, and carrying some heavy object, that dragged on the rocks, in her arms.

I could see her stooped figure, and the shadow of the thing that dragged. And there is no telling under Heaven the thoughts and the terrors that swept through me as to what that dragging thing might be.

But in an instant I saw what it was. It was a rather long, heavy plank, certainly of wood. She was about two hundred feet out on the rock wall by now, and I saw that she was launching the plank to the right of the wall, in the water of the lagoon. Before I could wonder or exclaim she herself had slipped in with it, her arms pale white from the shoulders of her dark bathing suit, wading out and guiding the heavy plank beside her.

No man who had read that mysterious script could doubt what her purpose was. She had gone fourteen rods out on the wall, and then she had turned to the right into the lagoon. Plainly she was searching for Jason’s treasure.

She, too, knew the key. In that same flash of time, I understood the look of intent I had seen on her face earlier that night. She had kept her resolve—even now she was herself trying to sound the mystery of her uncle’s disappearance. I understood her own exultation when I had talked of my many scientific plans, and how I lacked means to carry them out. Even then she had likely been working on the cryptogram. It was wholly possible that either Nealman or herself had encountered a copy of the script in the old house, and they had worked on it together.

But there had been some sort of a guard put over Jason’s treasure! With what right had we been so smugly certain that the old legend was not true—that there was not still some evil, tentacled monster of the deep left to slay and drag to his cavern those that dared to penetrate the lagoon. Even now she was wading further and further from the rock wall. I could see just her head and the top of her shoulders above water, the heavy plank still guided beside her.

Fear is an emotion that speeds like lightning through the avenues of the nerves. In the instant that these thoughts went home—thoughts that would have taken moments to narrate in speech but which whipped through the mind in the twinkling of an eye—I plumbed the utter depths of fear. There can be no other word. The gray expanse seemed the waters of death itself; the whole scene, in the gray of dawn, was eerie, savage, unutterably dreadful. And the girl that had come to be my own life was even now wholly within the power of any monstrous foe that should leave its cavern to attack her.

Why had we been so sure! Why hadn’t we guarded those deadly waters every hour, day and night. Every day teaches that many things that seemed incredible a day ago are true: how had we dared to be so arrogant in regard to the legend of the lagoon. Even when three men, one after another, had disappeared without trace we had refused to change our ancient habits of thought: we had still refused to believe. I knew now the fate of the missing men. They had gone in search of Jason’s chest—and the treasure guard that dwelt in the lagoon had put them to death. And just before my eyes the girl I loved was following the path they made, making the same quest.

And in that breathless, never-to-be-forgotten moment, I heard a resounding splash of water. Against the craggy, opposite shore the water flew far and white as some living thing that had been concealed in the far crags dived toward her through the still waters of the lagoon.

The whole scene had seemingly occupied less than a second. Already, before I could breathe, I was leaping down the corridor towards the stairs. I called once for help—a door behind me opened. Then I was out in the gray dawn, racing toward the lagoon.

There seemed no interlude of time between the instant that I saw that splashing water and that in which I had plunged full into the gray depths myself. In reality there was a space of several seconds—the gray light showed me that the drama of the lagoon had progressed immeasurably further. The girl was fifty or sixty feet from the rock wall now, just her head showing above water, her arms locked tight about the plank and facing her approaching foe. And something that swam swiftly made streaming ripples toward her.

I swam with amazing ease and swiftness. The terror, innate love of life, were all forgotten in the hope that I might reach Edith’s side in time. And now, by the gray light of dawn, I saw that her foe was upon her.

They were struggling with a desperate frenzy, and for an instant the splashing water almost obscured them. The plank had been torn from her grasp, and by some circumstance had been sped hopelessly out of her reach. And now, the water clearing from my eyes, I could determine the identity of her assailant. No matter what further fate the lagoon had in store for her, this foe was human, at least. Terrible and drawn with passion as it was, I saw the face of Major Kenneth Dell, the man who had disappeared the preceding night.

I yelled, trying to give hope. Already I was almost upon them; and Dell had released his hold of the girl. Whatever had been his purpose it had been forgotten in the face of some greater extremity. Their fight was no more with each other: rather they seemed at death grips with some resistless foe that tore at them from beneath the waves.

I saw Dell’s face. An unspeakable terror, that of one who in wickedness goes down to an awful death, was on his face. It was such a terror as men can know but once, for they never live to tell of it, and which blasts the heart of any one that beholds it. No artist, delving into the abnormal, could have portrayed that fear. It was a thing never to forget, but ever to see again in dreams.

Edith was terrified too, but such a terror as Dell knew was impossible for her. The fear of death that curses a godless man is perhaps the most dreadful retributive force in this world or the next, and Dell knew it to the full. No one who had seen his face could doubt but that all the iniquity of a long life had been atoned for, in one little moment, in the scales of justice. But only a measure of it could oppress her. The only fear that her fine young soul could know was that born of the elemental love of life. And with what seemed to be a final effort she raised her head to call a warning to me.

But even if I had heeded it, it would have come too late. I saw the heads of the man and woman in front of me go down as if drawn by quicksand. And there was no escape for me. The death that dwelt in the lagoon had already seized me in its resistless grasp.

But the guard over Jason’s treasure was not merely some monster implanted from the sea, a mortal thing that years could claim or muscular strength oppose. Rather it was a power that had dwelt there since the world’s young days, ever claiming tribute, and which would continue on until the very sea itself was changed. The demon that had hold of me was merely that of rushing waters. They swept me forward and sucked me down with remorseless force.

There was a sink-hole in the floor of the lagoon. No wonder the water that rushed in at high-tide had seemed to go so quietly away. I was being carried down a subterranean outlet, through some water passage under the rock wall, and into the open sea.