It was the second day of Wakefield's and Meredith's enforced but none the less interesting detention on board the mystery ship. Q 171 was well out into the North Sea, bound for a certain position a few miles to the west'ard of the now famous Horn Reefs Lightship. The sea was calm, a light breeze blew from the west'ard, while the sky was filled with small fleecy clouds drifting slowly athwart the lower air-currents--an indication of a forthcoming change of wind. The three officers, clad in black oilskins to keep up the rôle of Hun pirates, had been sitting on the cambered edge of the base of the dummy conning-tower, yarning of times not long gone and holding forth wondrous theories of what might happen in the seemingly far distant epoch after the war. "Small quick-firers," declared Morpeth, as the rumble of the sharp reports grew louder and louder. "None of our M.L.'s in action by any chance, I hope?" Slinging his binoculars round his neck, Morpeth, with an agility that his ponderous frame belied, clambered to the domed top of the conning-tower, reckless of the fact that his weight was causing the frail metal-work to "give" ominously. Bringing his glasses to bear upon a faint dot just on the horizon, Morpeth made a long and steady scrutiny. "Merchant vessel--tramp, by the look of her--chased by a Fritz," he reported, "Unhealthy work--for Fritz. I'll keep her on my lee bow a bit. It's no use butting in too soon. Too much dashed hurry spoils everything." At sixteen knots Q 171 held on, with the apparent object of joining in the chase and cutting off the fleeing merchantman. Quickly the chase came in sight--a bluff-bowed, wall-sided tramp, with an elaborately camouflaged hull. "Confounded scheme that razzle-dazzle," commented Morpeth. "Meet three or four in a crowded waterway, and you begin to wonder whether you'll see mother again. Can't tell whether they are bows on, or what. Fancy we've got her cold, though. For'ard gun, let her have it." The bow-chaser spat viciously, sending a shrieking missile within a hundred yards of the tramp, which, badly on fire aft, was still proudly flying the Red Ensign. Her funnel, hit about six feet above the deck, was showing signs of collapse, being supported only by the wire rope guys. Making a bare eight knots, she was evidently at the mercy of the pursuing U-boat, which, capable of doing eighteen on the surface, was slowing down after the manner of a cat playing with a mouse. Q 171, firing rapidly, but deliberately planting her shells wide of the merchant vessel, now turned twelve points to port. This had the effect of bringing her into a decidedly convergent course with that of the U-boat. The latter, probably "smelling a rat," or taking exception to what appeared to be another of her kind "spoiling the game," edged away to starboard, at the same time hoisting a signal.