They knew it was only a ruse to make them betray themselves, prompted by their enemy's keen anxiety to answer the summons, and they stood behind the boiler perfectly still. _Bur-r-r-r!_ "So you will not speak," snarled Von Dussel. "Very well, I am going to answer that message. I shall have a Browning pistol in one hand and the receiver in the other. You had better look out; you will never leave this room alive, either of you." Dennis, groping silently in front of him along the brick base in which the boiler was fixed, had found a heavy screw wrench, and, repeating his former manoeuvre, hurled it this time to the opposite end of the engine-room. It dropped with a loud clang; but Von Dussel was on his guard, and before he fired he switched his light on for an instant, and Dennis pulled the trigger of the rifle. It was only for a second's space that Dennis saw the man with his hand raised, and he could not repress a fierce shout of joy as a Mauser bullet dashed the Browning pistol from Von Dussel's hand. "Perhaps we English are not such fools, after all!" he laughed. But when the spy's voice answered him, it was from the opposite side of the room. "That remains to be seen," was his reply. "I tell you, you will not leave this place alive. The brewery is mined, and I am going to fire the charge. Good night. I will send Madame Dashwood a field post card to-morrow!" In vain Dennis had pulled on the trigger while he spoke, the rifle pointed in the direction of the voice. That cartridge had been the last one; and as they heard the heavy door bang for the second time that night, they knew that the man had gone and would keep his word! "Dennis, boy," said Bob quickly, "I'm rather afraid our number's up, after all. I'm useless with this leg, but where there's life there's hope. There's a permanent ladder at the end of this hole. Give me my crutch again, and, meanwhile, see where it leads to." Dennis did not require telling twice. "You're right, Bob," he said. "There's death on the other side of that door, so it's wasting time to try whether that hound has fastened it or no." And while he spoke he flashed his own pocket torch to the far end of the engine-room. "You'll be able to pick your way, and I'll be back in a shake," he concluded, tearing along the floor and bounding up a permanent ladder to the next storey. A circling sweep of his invaluable light showed the lad a low-ceilinged room corresponding to the one he had just left, and a cool wind blowing in from somewhere reminded him of his adventure in the German dug-out, and the friendly passage he had discovered. "Come on, Bob!" he called down the ladder. "I'll be back in a minute and give you a hand. We'll do the beggar yet." He bounded through the door which his light revealed, and found himself in the open air upon an iron gallery running along the outside of the building.