Sherlock kicked his feet against a rock and thought over all the information he had gathered about the Utway affair. He hoped that the print he was making would show without question the full villainy of the twins. If it did not, it would leave him in a predicament. Mr. Colby had not seen either of the Utway twins, who had made their ways back to their bunks without capture. Yes; the picture _must_ be a good one. Sherlock rose and went back into the dark-room.
With all the skill and care of which he was master, Sherlock Jones toiled over the developing of the first print of the raiding scene. Eagerly he bent over the developing bath as dark edges began to take shape on the bit of white paper. Slowly, slowly, the details melted into being, seeming to spring from the waters above the print. Now! The boy switched the print into the fixing tray, turned on the white light, and scrutinized his handiwork.
One glance, and he was ready to cry out with disappointment. He bit his lip. The explosion of the too-generous quantity of flashlight powder had startled him, and in his haste, unsure of his hearings in the darkness, he had twisted the camera on its tripod so that none of the action was visible. Diagonally across the picture ran the rear flap of the tent. The head and pillow of Mr. Colby showed with clearness, but the forms of the Utway twins and Alexander the frog were cut off by the expanse of the tent-fly. All that the picture revealed was a peaceful night-scene in one corner of Tent Fifteen—nothing more.
Had Sherlock not reminded himself that a good detective never gives way to emotion or shows in his features the state of his feelings, he might have stamped up and down the dark-room, raving at his failure. As it was, he controlled his disappointment as best he could, and patiently went over the picture a second time, to make sure that no detail had escaped his notice.
He was rewarded. In the upper corner of the print was something which at first glance he had not seen. It appeared to be an arm, the hand gripping one of the tent-ropes, the upper part near the body cut off by the edge of the negative. With growing excitement, Sherlock drew from his pocket the small magnifying lens he carried with him at all times. Taking the wet print into the outdoor sunshine, he focussed his glass on the mysterious detail. It _was_ an arm—and the lens showed plainly a mark by which a detective could distinguish this arm from all other arms in the vicinity. Upon the fleshy part of the under forearm was tattooed the sketchy design of an American eagle with outstretched wings.