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.
His impulse was to lift up a shout of thankfulness at the sight of another iron ladder, obviously leading into the yard below. To make quite certain that the way was clear he ran towards it, and stole cautiously down for a short distance, trying to penetrate the intense blackness in quest of any sign of Von Dussel.
All at once his feet dropped into nothingness, for, unknown to him, an English shell had carried away the rest of the ladder a week before, and, clutching wildly at the last step, he clung there, dangling in space!
To let go, even had he known the distance between him and the ground, was absolutely unthinkable with his brother helpless and unwarned within the building, and though the explosion of the mine might happen any moment, his one and only effort was to get back by sheer strength of arm and return to Bob's assistance.