The woman picked up one of them and removed the parchment. Before she drew the stopper she donned thick glasses and a mask for her face, the two Orientals doing the same. They were evidently dealing with some very dangerous poison. The stopper was removed and a few spots of the acid dropped on the copper disc. A white smoke arose, which, small as it was, filled the air with a pungent odor. Almost immediately the acid was wiped off and the odor ceased. Only just a whiff of it reached Geoffrey's nose, but it turned him faint--giddy for an instant. What was going to happen next? CHAPTER XLV BAFFLED Geoffrey had not long to wait. From where he was standing he could see down into the vault perfectly well. He would have been better satisfied had he understood what those people were talking about, but their words conveyed nothing to him. On the floor of the vault the queer-looking machinery was spread out, and to the ends of the india-rubber tubes wires were attached. No sooner had this been accomplished than the woman, after giving some rapid instructions to her allies, left the vault. She was so quick that Geoffrey barely had time to conceal himself behind a pillar before she passed him. The woman was masked and disguised beyond recognition, but Geoffrey had no need to be told who she was. He knew that he was in the presence of Mrs. May. And, despite his knowledge of her cleverness and resource, he found himself marveling to see her display so fine a knowledge of the house. The woman passed along, dragging a number of fine light wires after her. The other ends of the wires were attached to the queer-looking apparatus in the vault. Mrs. May went along the passages, along the corridor, and up the stairs as if she had been accustomed to the house all her life. Surely she must have been here many times before, or she would not have exhibited such fearless confidence. The idea of the black, gliding figure creeping about the house in the dead of night filled Geoffrey with loathing. All the same, he did not neglect his opportunities. He followed swiftly and silently until he came to the main corridor on the first landing. Here, to his surprise, the woman turned into one of the bed-rooms, the room used by the head of the house. She closed the door behind her. What to do next? But Geoffrey was not long in doubt. Ralph was standing by his side, a dark lantern in his hand. "Where did she go?" he whispered. "You heard her, then?" asked Geoffrey. "Of course, I heard everything. I see with my ears. Naturally you guessed who she was. But what room did she go into?" "My grandfather's." "So I expected. But she means to visit all the rooms in turn. You need not be afraid, she will be there for some minutes. What do you see outside?" Geoffrey made a close examination with the lantern. "I see a tangle of small wires on the floor," he said. "They come up from the vaults." "Where they are attached to a queer-looking instrument?"