Still that's hardly likely."

"But why are you so sure it was done by a child?"

"Why! Look at the height. These old-fashioned bricks are little more than two inches thick; there are twenty courses from the ground to the sketch if we call it so; that gives a height of three and a half feet. Now, just imagine you are going to draw something on this wall. Exactly; your pencil, if you had one, would touch the wall somewhere on the level with your eyes, that is, more than five feet from the ground. It seems, therefore, a very simple deduction to conclude that this eye on the wall was drawn by a child about ten years old."

"Yes, I had not thought of that. Of course one of the children must have done it."

"I suppose so; and yet as I said, there is something singularly unchildlike about those two lines, and the eyeball itself, you see, is almost an oval. To my mind, the thing has an odd, ancient air; and a touch that is not altogether pleasant. I cannot help fancying that if we could see a whole face from the same hand it would not be altogether agreeable. However, that is nonsense, after all, and we are not getting farther in our investigations. It is odd that the flint series has come to such an abrupt end."

The two men walked away towards the house, and as they went in at the porch there was a break in the grey sky, and a gleam of sunshine on the grey hill before them.

All the day Dyson prowled meditatively about the fields and woods surrounding the house. He was thoroughly and completely puzzled by the trivial circumstances he proposed to elucidate, and now he again took the flint arrowhead from his pocket, turning it over and examining it with deep attention. There was something about the thing that was altogether different from the specimens he had seen at the museums and private collections; the shape was of a distinct type, and around the edge there was a line of little punctured dots, apparently a suggestion of ornament. Who, thought Dyson, could possess such things in so remote a place; and who, possessing the flints, could have put them to the fantastic use of designing meaningless figures under Vaughan's garden wall? The rank absurdity of the whole affair offended him unutterably; and as one theory after another rose in his mind only to be rejected, he felt strongly tempted to take the next train back to town. He had seen the silver plate which Vaughan treasured, and had inspected the punch-bowl, the gem of the collection, with close attention; and what he saw and his interview with the butler convinced him that a plot to rob the strong box was out of the limits of enquiry. The chest in which the bowl was kept, a heavy piece of mahogany, evidently dating from the beginning of the century, was certainly strongly suggestive of a pyramid, and Dyson was at first inclined to the inept manoeuvres of the detective, but a little sober thought convinced him of the impossibility of the burglary hypothesis, and he cast wildly about for something more satisfying. He asked Vaughan if there were any gipsies in the neighbourhood, and heard that the Romany had not been seen for years. This dashed him a good deal, as he knew the gipsy habit of leaving queer hieroglyphics on the line of march, and had been much elated when the thought occurred to him. He was facing Vaughan by the old-fashioned hearth when he put the question, and leaned back in his chair in disgust at the destruction of his theory.

"It is odd," said Vaughan, "but the gipsies never trouble us here. Now and then the farmers find traces of fires in the wildest part of the hills, but nobody seems to know who the fire-lighters are."

"Surely that looks like gipsies?"

"No, not in such places as those. Tinkers and gipsies and wanderers of all sorts stick to the roads and don't go very far from the farmhouses."

"Well, I can make nothing of it. I saw the children going by this afternoon, and, as you say, they ran straight on. So we shall have no more eyes on the wall at all events."

"No, I must waylay them one of these days and find out who is the artist."

The next morning when Vaughan strolled in his usual course from the lawn to the back of the house he found Dyson already awaiting him by the garden door, and evidently in a state of high excitement, for he beckoned furiously with his hand, and gesticulated violently.

"What is it?" asked Vaughan. "The flints again?"

"No; but took here, look at the wall. There; don't you see it?"

"There's another of those eyes!"

"Exactly. Drawn, you see, at a little distance from the first, almost on the same level, but slightly lower."

"What on earth is one to make of it? It couldn't have been done by the children; it wasn't there last night, and they won't pass for another hour. What can it mean?"

"I think the very devil is at the bottom of all this," said Dyson. "Of course, one cannot resist the conclusion that these infernal almond eyes are to be set down to the same agency as the devices in the arrowheads; and where that conclusion is to lead us is more than I can tell. For my part, I have to put a strong check on my imagination, or it would run wild."

"Vaughan," he said, as they turned away from the wall, "has it struck you that there is one point—a very curious point—in common between the figures done in flints and the eyes drawn on the wall?"

"What is that?" asked Vaughan, on whose face there had fallen a certain shadow of indefinite dread.

"It is this. We know that the signs of the Army, the Bowl, the Pyramid, and the Half moon must have been done at night. Presumably they were meant to be seen at night. Well, precisely the same reasoning applies to those eyes on the wall."

"I do not quite see your point."

"Oh, surely. The nights are dark just now, and have been very cloudy, I know, since I came down. Moreover, those overhanging trees would throw that wall into deep shadow even on a clear night."

"Well?"

"What struck me was this.