It was one of those marvellous underground constructions for which the Germans seem to have a positive genius. The chalk had been excavated for trench building, the walls were boarded, and square balks of timber supported the roof in a double row of pillars. He could not count the cases of ammunition--there were so many--nor the stacks of rifles that were stored in the place, but he saw enough to convince him that he had made a very important haul, if only things were going well above ground. The distance he had fallen surprised him when he mounted the steps, but the steel door resisted all his efforts to open it, and though he thundered with his fists, there was no response from the other side. "I've got to get out of this somehow," he thought, and, descending to the floor again, he made a minute inspection of the vast dug-out without finding any means of egress, until he came to an open case of rifle ammunition, from which several packets of cartridges had been removed. As he read the description printed on the others he felt cold air blowing on him from somewhere not far away. At first he thought there must be some hidden ventilation shaft, but the draught was low down and fluttered the tatters of his abbreviated tunic. "It's a jolly odd thing," he murmured, turning his light in the direction of the current. "Surely there is not another dug-out below this one?" He passed round the angle of some piled-up boxes stamped with strange hieroglyphics, and then he stood still, for there was another door, the entrance to a gallery, as he saw in a moment. But this time it led upward in a rather steep slope, and the floor was marked with the print of heavy boots, showing that the passage had been well used. "I suppose it would take a month of Sundays to come across some revolver ammunition, and then the chances are it wouldn't fit these French chambers," he thought, examining the commandant's second revolver, which had only one charge left. "Anyway, I must find where this leads to." And, veiling the light with his fingers, he entered the gallery. The sides had been roughly smoothed and faced by the pioneers' shovels, and he shivered involuntarily, for it was cold. Making no noise, he crept for some distance in a straight line, until he came to a right-angle bend in the gallery, which he followed for sixty or seventy yards, and then switched off his torch as a loud explosion, not far ahead, seemed to drive the air against his cheeks, followed by the acrid odour of a German cartridge. For an instant he believed himself to have penetrated an enemy sap, but now he knew that somewhere close in front lurked a German sniper! Dennis Dashwood dropped on to one knee and peered along the passage. A faint light filtered through the darkness and a voice boomed dully.