By stratagem Derek might do something. Unceremoniously pushing aside the still bewildered coxswain, and ordering the engineer to "let her rip for all she's worth", Derek swung the helm hard over until the motor-boat headed straight for the long, low-lying, sinister hull. "Full throttle!" yelled Daventry. "Lie down, men, all of you." [Illustration: SHE PRESENTED A PUZZLING PROPOSITION TO FRITZ] M.B. No. 1164 B, gathering way, travelled faster than ever she had done since her acceptance trials. Her long, lean bows lifted clean out of the water, while her stern squatted deeply into the trough of her wake, and feathery shafts of spray shot out far and wide of her knife-like stem. Viewed "bows on" she presented a puzzling, nay alarming, proposition to Fritz, whose nerves were already unstrung through the effects of half a dozen narrow squeaks. All he saw was something approaching at terrific speed. He knew that there were mosquito craft that had their stings in their tails, and depth-charges were his great aversion and terror. Nearer and nearer drew the motor-boat. Derek's resolution increased with every revolution of the propeller. He had started with the idea of "putting the wind up Fritz", but now he meant to hurl the boat bodily at the submarine, and take his chance of being picked up. A 35-foot boat travelling at seventeen knots would by its momentum shatter some of the hull plates of the submarine, but at the same time her bows would crumple up like brown paper. Once and once only did the Lieutenant turn his head and glance at his crews. For novices they were behaving splendidly, lying stiffly, yet alertly, on the cockpit-gratings, although they could not resist the temptation of looking over the side to "see how things were going". Not a man showed a trace of fear. It was an expression of determination, of really "doing his bit" that showed itself in the knit brows of every member of the crew. The U-boat made no attempt to do further damage to the fishing-boats. Two men at the quick-firer abaft the conning-tower swung the weapon round and let fly at the elusive target presented by the bows of R.A.F. 1164 B. Derek saw the flash, and distinctly heard the screech of the projectile ere it burst four hundred yards astern. It was the last show. Already the U-boat's nose was dipping. The gunners, abandoning their weapon, bolted precipitately for the after-hatchway. With a resounding clang the water-tight metal cover fell in its appointed place, and the long, unsightly grey hull slithered beneath the waves in a swirl of froth and foam.