Near the edge of the grass and parallel to it, there was an indentation a little over an inch wide and about the same depth. It extended in a straight line for perhaps nine inches, and what could have caused it was a puzzle to Gimblet. The turf was unbroken, and it looked as if an oblong, narrow, heavy object had rested there, sinking a little into the ground so as to leave this strange mark. Gimblet rubbed his forehead pensively, as he looked at it. Suddenly as his introspective gaze wandered unconsciously over the ground before him, his attention was arrested by a second mark of the same perplexing shape, which he could see behind a rose-bush, more than half-way across the bed. Stepping as near the hedge as he could, the detective proceeded to examine this duplicate of the riddle. It seemed absolutely the same, though deeper, as was natural on the soft mould, and he found, by measuring, that it lay exactly parallel to the other. What could it be, he asked himself. A moment later, still another and yet stranger impression caught his eye. It was about the same width, but not more than half as long, and rounded off at each end to an oval. It was situated about a foot from the deep indentation and rather farther from the holly hedge. A tall standard rose-tree, covered with blossoms of the white Frau Karl Drouski rose, grew near it, interposing between it and the house. Gimblet measured it with painstaking precision; then with the help of his measurements, he made a life-size diagram of it on the page of his notebook, and studied it with an expression of annoyance. He had seldom felt more at a loss to explain anything. At length he turned and went back towards the grass. "What a track I leave," he thought to himself, looking down ruefully at his own footprints. "What I want is--" He stopped abruptly as a sudden idea struck him; then a look of relief stole slowly over his face, and he permitted himself a gratified smile, "To be sure!" he said, and seemed to dismiss the subject from his mind. Indeed, he turned his back upon the rose-bed, and strolled away by the side of the hedge, which was of tall and wide proportions, providing a spiky, impenetrable defence against observation, from the outside, of the rectangular enclosed garden. Half-way along it he came upon an arched opening. Passing through this, he found himself in an outer thicket, and immediately upon his right hand beheld a small shed, which stood back, modest and unassuming, in a leafy undergrowth of rhododendrons. Gimblet pushed open the door and stepped inside.