"But, sir," protested Frank, "could he not have steered us the same distance, but in another direction? Is it not possible that when we come up we may be right in a nest of the enemy's ships, or under the guns of their fortifications?" "It is possible, yes," replied Lord Hastings, "but you are wrong. You are both letting your imaginations run away with you. No; I am sure the man is up to no trick." "At least, sir," protested Frank, "do not rise clear to the surface without looking about through the periscope." "That is good advice, and it shall be heeded," said Lord Hastings. "Mr. Templeton, you may give the command to rise." Jack saluted and did as commanded, and with the periscope just above the water, the D-16 became stationary. Frank put his eye to the periscope and started back with an exclamation of dismay. At the same moment the German officer sprang to the signal tube, and, in perfect English, gave the command to rise to the surface. Jack took in the situation upon the instant and sprang toward the German even as he leaped toward the tube. But he was too late, and before he could countermand the order, the D-16 floated upon the surface of the water. Jack, in the meantime, was grappling with the German officer, who had drawn a concealed revolver and was attempting to bring it to bear upon Lord Hastings. Frank sprang to his assistance, and Lord Hastings, unmindful of the struggle, and thinking only of the mistake he had made, stepped quickly from the compartment, and opening the conning tower, made his way to the bridge. And there, he, too, started back in dismay, and no wonder. For what his eyes beheld was this: Dead ahead rose the sheer walls of a massive fortress, the powerful guns of which swept the narrow canal for miles. And at either side, with the D-16 squarely between them, four battle cruisers rode gently on the waves. Lord Hastings took one quick look at the flags that floated above the big battle cruisers, then dived hurriedly below. For the flags that fluttered in the breeze were the flags of Germany! CHAPTER XI. AT CLOSE QUARTERS. Below, Jack and Frank were still struggling with the German officer, but Lord Hastings had no time to lend them a hand. He raised his voice in a shout, and the crew came running at his command. "Submerge instantly!" he cried. But already sharp eyes aboard the German cruisers had caught sight of the submarine, and even as she sank suddenly from sight a single gun roared. The aim of this particular gunner was excellent; for the periscope of the D-16 was carried away as clean as a whistle. Lord Hastings, who had been peering through it from below, was instantly aware of what had happened, and he immediately rushed to the compartment where the searchlight was placed and turned it on. This was now the only eye the submarine had with which to look for danger ahead.