There had been signs of activity in Hun naval circles--activity forced upon them by prompt and vigorous measures of the sea-dogs under the White Ensign. Zeebrugge was getting too hot to hold the German torpedo-boat flotillas that for months had existed under nerve-racking conditions in that Belgian port. Constant bombardments from the sea and from the air had made the Huns' new base so insecure that the German ocean-going torpedo-boats (craft that compare in point of size with destroyers, although the term destroyer does not figure in Hun naval reports) had been compelled to make a dash for the neutral defences of the Elbe, Weser and Jade. Existing conditions made it undesirable to sneak through Dutch territorial waters, and the only other way was by a circuitous course rendered necessary by the presence of a vast British minefield. The British Admiralty, out of consideration for neutral shipping, had advertised the limits of the danger zone, which was an aggressive minefield rather than a defensive one--in other words its base was situated close to the German coast, while its apex stretched westward far across the North Sea. Round this apex the German torpedo craft had to make their way. Knowledge of the attempted dash had reached the ears of the British Commander-in-Chief, and strong flotillas of destroyers were patrolling the length and breadth of the North Sea, their search assisted in broad daylight by seaplanes sent up from attendant parent ships. At night the difficulty of maintaining the cordon was enormously increased. A German boat might slip through in the darkness, while, even if discovered, her attackers would be under the disadvantage of making sure that she was not one of their consorts before opening fire. The "Audax" was operating in the high latitudes of the North Sea. In fact, if she held on the course for another five hours she would run ashore somewhere in the close proximity of The Naze of Norway. Two miles ahead and astern of her were other vessels of the same class, the line being continued until the chain of destroyers stretched across the North Sea from Scotland almost to Scandinavia. The Straits of Dover were similarly patrolled, while auxiliary destroyers swept the seas between the northern and southern limits, ready to head off the fugitives or bring them to action. Rolling fully dressed out of his bunk--for under these conditions it would be folly to turn in otherwise--Billy dashed on deck, followed by the Engineer-lieutenant, who happened to be the only officer in the ward-room not on watch.