Without motive power the submarine was helpless for under-water work. She could fill her ballast tanks, but it would be impossible to sink only to a required depth. She would sink rapidly until the tremendous external pressure of water would crush her thick steel hull like an egg-shell. "How long will it take you to make good defects?" demanded von Preugfeld of the thoroughly scared mechanic. "Half an hour--twenty minutes?" "I will try, Herr Kapitan. Perhaps in half an hour----" "Then get on with the task," almost shouted the excitable ober-leutnant. "First couple up the surface-cruising engines. Von Loringhoven, turn out the guns' crews. If that motor vessel comes in sight we must try and settle her before she uses her depth-charges, or it will be all up with us. Ten thousand curses on von Preussen for having got us into this mess!" Although scared himself, von Loringhoven could not help smiling at his superior's words. He realised that the spy had little or nothing to do with U 247's present predicament. It was just possible that the concussion caused by the bombardment of Aberspey might have set up a short circuit, but von Preugfeld would never admit that. At frequent intervals the U-boat's engines were stopped. The noise of the unseen motor vessel's exhaust alternately grew louder and fainter. Somewhere in that baffling mist was the danger. Engaged in a mutual game of maritime blind man's bluff the submarine and the submarine-hunter were groping for each other. At any moment a rift in the veil of fog might bring the adversaries almost broadside to broadside. Von Preugfeld glanced at the luminous dial of his watch. "Fifteen minutes more," he muttered. "Will it be in time?" CHAPTER VI PICKED UP "PULL starboard; back port!... Give way together!" ordered Lieutenant-Commander Wakefield, as the blunt bows of the U-boat appeared through the dispersing fog-bank. The men obeyed with a will. Almost in its own length the "tin" dinghy spun round and darted towards the pall of misty vapour. It was a dog's chance, and the men realised it, but they were not going to throw up the sponge without a determined effort to escape. Alas for the bold resolve! With a rapidity that was little short of miraculous for a vessel of her type, the U-boat turned to starboard. Then, with her engines reversed, she brought up dead with her bows within an oar's length of the M.L.'s dinghy. Right for'ard were half a dozen men clad in oilskins. One of them brandished a long boat-hook. "Game's up, Fritz," shouted an unmistakable Devonshire voice. "Be yu comin' quiet-like?" For a moment the men sat dumfounded. Then Wakefield laughed mirthlessly. "She's one of our new submarines!" he exclaimed. "And we've been engaging her by mistake. Good heavens, what a proper lash up! Make fast there!" The bowman threw a coil of rope, and as the boat swung alongside the giant submarine Wakefield leapt on board, followed by Meredith.