"We are as safe," said Rivers calmly, "as if we wore caps that rendered us invisible, as in the fairy tale. As they stand side by side at the window, the position of the light enables me to see them clearly. They _are_ Mr. Nisbet and Dr. Cooper. Provoking! What is it that Mr. Nisbet has just done? Why did you move, you fool of a doctor? But I guess what he did. He emptied the glass out of the window. Of course, of course; that was it. They have been making a chemical experiment, testing a liquid--to what end? Mr. Nisbet peers into the dark grounds, he stares straight at the hill upon which we are lying. Don't stir a finger. It is curious that criminals almost invariably overlook some slight circumstance which supplies the clew to their conviction. It has been so in thousands of cases. The window is closed, the blind is pulled down. See the shadows of the men as they approach and retreat, growing to monstrous proportions, dwindling to nearly natural size. The shadows of Fate. I suppose by this time the conference is at an end. It is. They separate. Each is in his own room. Ah, I see which room is occupied by Mr. Nisbet, and which by Dr. Cooper. The doctor gets into bed first. Out goes his light. Sleep the sleep of the just, doctor, if you can. Mr. Nisbet lingers; his is the greater stake. He is the principal, his companion is the tool. Take care, the pair of you; the dogs are on your track. Mr. Nisbet puts out his light; all the windows are masked except the window of the third room. Good-night, good-night." These ingenious theories filled me with wonder, and I accepted them as if they were proved testimony; and I am positive, from the remarks made by Bob and Ronald, that they also accepted them as I did. Rivers chuckled, and said: "It is a fine art, and we become masters only by long study. Now for Mme. Bernstein. She will not keep us waiting long." She did not. In a few minutes the gate was opened, and the old woman appeared. CHAPTER XXVIII. MME. BERNSTEIN REVEALS. Rivers went forward to meet her, and taking her hand, led her to where we were standing. Dark as it was I saw that she was greatly agitated, and the increase of our party did not lessen her agitation. "You perceive," Rivers commenced, "that it is as I said. There are four of us, and we are determined to know the truth about your master and what is going on in that gloomy house, which, as I just remarked to my friends, resembles a prison." "I will tell you everything," said Mme. Bernstein, her voice shaking with fear. "Why should I not, when you have promised to reward me? I have done nothing wrong."