By this time Lexy had reached the head of the stairs. Beside her was an open door, through which she could look, while she herself was hidden from view. Beyond it was, as she had thought, the cupola—a small octagonal room with windows on every side, through which the sun poured in a dazzling flood. There was nothing in the room except a white enamel table, a stool, a porcelain sink, and an open cabinet, upon the shelves of which stood rows and rows of bottles, each one labeled. Facing this cabinet, and with their backs toward the door, stood the two men—the doctor with his shoulders hunched and his hands clasped behind him, and Captain Grey, tall, slender, straight as a wand. “Materia medica—that is my art,” said the doctor. “I have devoted my life to it, and I have learned—a little. I have made experiments. A psychologist will offer to tell you why a man has murdered his grandmother. I can’t pretend to do that, but I can give that man a tablet which will make it practically certain that he _will_ kill his grandmother if they are left alone together for ten minutes.” “But, I say!” protested Captain Grey. “I can assure you that I have never made the experiment,” said Dr. Quelton, with a laugh; “but I could do it. I have learned that certain states of mind can be produced by certain drugs.” Captain Grey turned his head, so that Lexy could see his handsome, sensitive face in profile. “That seems to me a pretty risky thing to do,” he said, with a trace of sternness. “I hope, sir, that you don’t—” “Don’t give Muriel drugs that make her disposed to murder her grandmother?” interrupted the doctor, with another laugh; but he must have noticed that his companion was unresponsive, for he at once changed his tone. “No,” he said gravely. “I have made a particular study of Muriel’s case. She seriously overtaxed herself in her musical studies. Don’t be alarmed, my dear fellow—there is no permanent injury. It is simply a profound mental and nervous lassitude—obviously a case where artificial stimulation is required, until the tone of the lethargic brain is restored. I am able to do for her what, I feel certain, no one else now living could do. In this bottle”—he tapped one of them with his forefinger—“I have a preparation which would make my fortune, if I had the least ambition in that direction. Five drops of that, in a glass of water, and her depression and apathy are immediately dispelled. There is an instantaneous improvement in—” Lexy waited to hear no more. She slipped down the stairs as quietly as she had come up, hurried along the hall, and went into her own room again. Her knees gave way and she collapsed into a chair, staring ahead of her with the most singular expression on her face. She was, in fact, looking at a new idea, and it was not a welcome one. “No!” she said to herself. “It’s out of the question. It’s too dangerous. I can’t do it!”