The secret of the D-16 was known to only a trusted few besides the crew of the vessel--the King, Winston Churchill, and David Lloyd George, Chancellor of the Exchequer. Besides her ability to remain submerged, D-16 was also many knots faster than any other submarine. From a naval viewpoint, perhaps, the war up to this time had not progressed as favorably as had been expected. While the allied forces on the continent had been hemming in the Germans and their allies, driving them back from beneath the very walls of Paris, back across the Marne and across the Aisne, and while the legions of the Czar had been attempting to force a passage of the Carpathian mountains for an invasion of Hungary and Austria, and making determined assault within the borders of East Prussia, the British, French and Russian fleets had been practically inactive. True, there had been several important naval battles, but none which could be called decisive, although whatever advantage there was was with the British. The French, with the Austrian fleet cooped up in their base in the Adriatic, had little to do but to see that the Austrians were not allowed to escape. The Russian fleet had had one or two brushes with the Turks, but these were unimportant. In the North Sea England was having more difficulty. German submarines, from their base at Ostend, had made several successful raids into Dover harbor, on the British coast; three unfortified towns on the coast had been razed by German shells and German aeroplanes had been seen flying about in the vicinity of London. Huge Zeppelin balloons, upon which, England believed, the German Emperor planned to risk all should other means fail, had been seen over the British Isles, but had been driven off. One had been sunk. After this, England, ever fearful of an air raid, took heart, and agreed with the nobleman who said that a raid by air was not feasible. Besides the ships of war that had been sunk by the Germans, British merchant vessels had also been sent to the bottom by the enemy's submarines. But the main German fleet was cooped up in Heligoland and in the Kiel canal by the British blockade, which, in itself, was proof positive of Great Britain's naval supremacy. The Kaiser had no mind to give open battle to England on the sea. This was the situation, then, when submarine D-16 set forth from London, to do, with her new power, what damage she could to the enemy's fleet. One day, while the lads had been looking over the vessel, as she lay in drydock, they had seen a man run furtively from the place as they approached; but they were unable to catch him. A second time they had seen him, though not close enough to identify him. Although both had thought considerably of the matter, neither had mentioned it to the other, and it had been allowed to drop. Nor had they come upon the man again before they put to sea.