here was no sign of the man they had come to help. He was not in the laboratory, though the door had been locked from within and the lights left burning throughout.
With painstaking care they searched every nook and cranny of the large single room and were about to give up in despair when Tommy happened to observe an ivory button set into the wall at the only point in the room where there were no machines or benches at hand. Experimentally he pressed the button, and, at the answering rumble from under his feet, jumped back in alarm. Slowly there opened in the paneled oak wall a rectangular door, a door of large enough size to admit a man. From the recess beyond there came a breath of air, foul with the musty odor of decayed vegetation, dank as the air of a tomb.
"Ah-h-h!" breathed Frank. "So that is where Ed Leland is hiding! The secret retreat of the gloomy scientist!"
He spoke half jestingly, yet when he squeezed his stalwart bulk through the opening and flashed the beam of his light into the darkness of a narrow passage ahead he was assailed with vague forebodings. Tommy followed close behind and spoke not a word.
he passage floor was thick with dust, but the marks of many footsteps going and returning gave mute evidence of the frequency of Leland's visits. The air was heavy and oppressive and the temperature and humidity increased as they progressed along the winding length of the rock-walled passageway. The floor sloped, ever downward and, in spots, was slippery with slimy seepage. It seemed that they turned back on their course on several occasions but were descending deeper and deeper into the heart of the mountain. Then, abruptly, the passage ended at the mouth of a shaft, which dropped vertically from almost beneath their feet.
"Whew!" exclaimed Frank. "Another step and I'd have dropped into it. That's probably what happened to Leland."