At the same instant he rushed toward the door, and struck out at the nearer Japanese. The blow did not land. His wrist was caught in a grip like an iron clamp, and he found himself performing queer gyrations. The Japanese had turned his back toward Orme and swung the imprisoned arm over his shoulder. A quick lurch forward, and Orme sailed through the air, coming down heavily on his side. His arm was still held, and in a few seconds he was on his back, his assailant astride him and smiling down into his face. Orme struggled to free himself, and promptly felt a breaking strain on his imprisoned arm. The knee of the Japanese was under the back of Orme's elbow. A moderate use of the leverage thus obtained would snap the arm like a pipe-stem. This Orme realized, as he ceased struggling. The strain on his arm relaxed slightly, but the grip was maintained. "Jiu-jitsu," explained the Japanese in a tone that sounded gently apologetic. The other robber now stooped and ran his hands over Orme's coat. Finding the pocket-book, he took it from its inside pocket and went swiftly to a table. He produced from his own pocket a little electric hand-lamp, by the light of which he took rapid count of Orme's money. His eyes glittered; a wide scar on his forehead stood out whitely. Suddenly he gave a little cry and held up a single bill. He jabbered excitedly to his companion for a moment, then spoke quietly to Orme. "This all we want," he said. "We are not thief, see--I put other five-dollar bill in its place and leave pocket-book here." He thrust the selected bill into his pocket, put the fresh bill in the pocket-book, and laid the pocket-book on the table. "See here," said Orme, still prone, "what's the meaning of all this?" "Don't say." The Japanese smiled. He went over to the door. "Come," he said. The man astride Orme released his hold and sprang to his feet. Like a flash, both the Japanese disappeared. Orme jumped up. Seizing his pocket-book and his hat, he darted after his assailants. At the street entrance to the tunnel, he looked quickly in both directions, but his men were not in sight. Pursuit was futile. Slowly he turned back. He thought of notifying the police, but, after all, he was none the worse off--except for his promise to Poritol and Alcatrante, now involuntarily broken. He must explain to them as best he could. The marked bill had been of no consequence to him except as a focus of adventure. And he had had about as much adventure as he could expect for one evening. But the secret of the bill still tantalized him. Blindfolded, he had played in a game at which the others saw. It seemed unfair--as if he had some right to know the meaning of all these mysterious incidents. Why had Poritol wanted the bill so badly? Why had the desire to possess it driven the two Japanese to such extreme measures? Orme crossed the court and entered the lobby. The clerk looked at him curiously.