“It is dawn,” said Rouletabille. “And Old Bob is still at work. This old fellow is certainly industrious and we will go and have a peep at him at his labors. That will change our current of thought and I shall be able to get away from these horrors that are smothering me and driving me half wild.” And he heaved a long sigh. “Will Darzac never return!” he murmured, more as though he were speaking to himself than to me. A few moments later we had crossed the court and had descended into the octagon room of the Tower of Charles the Bold. It was empty. The lamp was burning on the work table, but there was no sign of Old Bob. “Oh!” cried Rouletabille. He picked up the lamp and carried it from place to place examining everything around him. He tried in turn the lock of every little window which opened from the walls of the basement. Nothing had changed its place, and all was arranged in order and scientific etiquette. While we were looking around at the bones and shells and horns of the prehistoric ages, the “hanging crystals,” the rings made out of bone, the buckles formed from teeth, and the other treasures of the savant, we came to the little desk-table. There we found the “oldest skull in the history of humanity”; and it was true that it had been spattered with the red paint of the wash drawing which M. Darzac had set to dry upon that part of the desk which faced the window and was exposed to the sun. I went from one window to the other and shook the iron bars in order to assure myself that they had not been touched nor tampered with in any way. Rouletabille saw what I was doing and said: “What are you about? Before thinking about how he could have gotten out at the windows, wouldn’t it be better to find out whether he went by the door?” He set the lamp upon the parapet and looked for traces of footprints. Then Rouletabille said: “Go and knock at the door of the Square Tower and ask Bernier whether Old Bob has come in. Ask Mattoni at the postern and Pere Jacques at the iron gate. Go, Sainclair--quick!” Five minutes after I went out I was back with the information. No one had seen Old Bob in any part of the fortress. He had not passed by anywhere. Rouletabille had his face close to the parapet. He said: