Patsy stepped in and closed the door, leaving it unlocked, lest he might have occasion to retreat hurriedly. The closing of the door left the hall and stairway in darkness--barring a single thread of artificial light that now caught his eye. It was a vertical thread in the side wall, some two feet from where he was standing. “Electric light,” thought Patsy, listening again. “The store is not lighted. Nor does the store run back as far as this. The door leading into the store from this hall is farther in. There must be a lighted room back here, all the same, or this chink--by gracious, it’s a panel door.” Thrusting his nails into the crevice through which the light had shone, Patsy had felt a section of the wall slip noiselessly to one side, revealing a secret panel so skillfully constructed as to defy ordinary inspection. It revealed, moreover, something of far greater significance. A flight of steps led down to a brightly lighted basement in the extreme rear of the building. It was walled in like a tomb, however, with no sign of a window. On the cement floor stood a large horizontal engine of peculiar construction, so peculiar that Patsy could not imagine for what it was used, or why it was there. Near by on a rack was a metal cylinder about two feet long and ten inches in diameter. Each end had a movable metal cover. Around both ends, moreover, was a flange of thick felt. On a narrow table near the farther wall, one of them spread open evidently for inspection, and so placed that its folds hung nearly to the floor, lay two costly Persian shawls. The instant Patsy’s gaze fell upon them, the truth began to dawn upon him. “Great guns!” he exclaimed mentally. “The two shawls mentioned by Goulard. He did not bring them here, however. There is a connection between this cellar and the department store. That’s a dead open-and-shut cinch, and it’s operated in some way with this engine. By gracious, I’ll have a closer look, if it takes a leg!” Patsy had seen, of course, that this subterranean chamber then was deserted. Placing the panel exactly as he had found it, Patsy crept down the steps and gazed around. “I have it,” he muttered. “This interior wall has been built across the original basement so as to form this chamber, and at the same time prevent detection by persons in the other part of the basement, who would naturally suppose it extended back no farther than this inner wall. It must be to the other part of the basement that Chick descended. He still must be there, too, unless----” That there was no alternative, that his suspicions from the outset had been correct, that he had trapped himself also, and was up against a sudden, desperate situation--all flashed over Patsy on the instant, when his train of thought was broken by sounds that sent a momentary chill down his spine.