Full fifteen steps were descended before the three men gained a level passage. Placing his hand on one of the walls the Sub made the discovery that the stonework was warm. On the other side of the wall was, apparently, the large stove used for heating the whole house. Suddenly the lamp went out. "A thousand apologies!" exclaimed Klostivitch. "It was the draught. Have you a box of matches by any chance?" "Yes, I have," replied the Sub, secretly rejoicing that the extinguishing of the lamp was by accident, not design, and that the Russian seemed as anxious as the others to rectify matters. He unbuttoned his heavy greatcoat, and, removing his gloves, fumbled for his silver match-box. "Here it is, monsieur," he exclaimed, extending his hand. He waited a few seconds, under the impression that the Russian was groping for the proffered article. Then he repeated the announcement, adding, in a tone of involuntary impatience: "Where are you?" "Here," replied a mocking voice above his head, "blundering busybodies that you are! You are securely trapped this time, and you will have good cause to repent of your unwarrantable and interfering curiosity." Then came the dull thud of a heavy stone slab falling into position, and Fordyce and the petty officer found themselves prisoners in the cellar of the mysterious house. CHAPTER XXIII Trapped "'Tain't quite all ship-shape, is it, sir?" enquired Petty Officer Chalmers, who, ignorant of the Russian language, could only base his surmise upon the fact that Klostivitch had suspiciously made himself scarce. "I'm afraid not, Chalmers," replied Fordyce. "We took too much for granted, and pal Vladimir has sold us a dog. Don't move till I strike a match; there may be boobytraps about." The glimmer of the lighted match revealed the lamp. Either by accident or design Klostivitch had left it on the floor. "Proper Tower o' London sort of show," commented Chalmers, examining his surroundings by the feeble glare. "Look, sir, that's where the old rascal shinned up." He indicated a number of iron rungs clamped into the wall, while immediately above was a square opening in the stone ceiling, over which had been lowered a huge block of granite. "Come along, sir," continued the petty officer. "Let's get back to the steps. Maybe the slippery reptile hasn't had time to shut the door." Quickly the two men ascended the flight of steps, only to find their exit barred by a securely bolted door. Vainly the burly petty officer thrust with his shoulder against the firmly-held barrier. "Hist!" exclaimed Fordyce. From the other side of the door came the Russian's mirthless laugh. Then, finding that his captives had at least temporarily desisted from their efforts he shouted: "Don't forget to keep the stove burning, you English imbeciles--that is, _if the diamonds are what you think they are._"