He stepped to the periscope, which Jack relinquished to him, and peered ahead. Beyond the cruiser he could make out the periscope of another submarine. Calculating the distance. Lord Hastings gave the order to submerge four fathoms. Then the D-16 dashed in the direction of the submarine that was seeking to destroy the Russian. Running at 30 knots, the D-16 soon came upon its prey. A dim bulk suddenly loomed up ahead, some distance higher in the water. "It's the enemy," said Frank, after a careful scrutiny. "All right," said Lord Hastings. "Give her a shot before she discovers our presence. We can't miss at this distance." Through the heavy glass in the bow of the submarine Frank watched the effect of the shot. The German submarine staggered suddenly in her stride, then, without a sound, disappeared from sight. Frank returned to Lord Hastings' side. "She's gone, sir," he said quietly. Lord Hastings turned to Jack. "We'll go to the surface at once," he said. Hardly had the D-16 bobbed up from beneath the water, when there was a loud boom from the Russian ship now but a short distance away, and a shell screamed overhead. "Run up the British flag, quick, Mr. Templeton," ordered Lord Hastings. A moment later the Union Jack fluttered aloft. Came another shot from the Russian, and a second shell screamed near. "The fools," cried Lord Hastings angrily. "What do they mean by that?" "They think we are trying a ruse to get near them, I suppose," replied Frank. "They are unable to tell we are not the same submarine that followed them." "True," said his commander, "I hadn't thought of that. But how are we to let them know who we are?" "Well, my idea would be to run up a flag of truce," said Frank. "Then we can explain." "Good," exclaimed Lord Hastings. "Run up a flag of truce at once." It was the work of but a few seconds to raise a white flag, and when it had straightened out before the brisk breeze, there was no further shot from the Russian cruiser. Soon a boat put over the cruiser's side, and manned by a well armed crew, came toward the D-16. Within hailing distance an officer arose and cried out something in a tongue unintelligible to any on board. "Speak English!" Lord Hastings called back. "I can't understand you." The next words came in halting English. "Who are you?" "British submarine, D-16!" Lord Hastings called back. "Then why did you fire at us?" "We didn't. You were fired upon by a German submarine, which we have just sunk. Will you come aboard?" "Yes," was the reply, and the little boat drew closer. A moment later a man in the uniform of the Russian navy stepped over the side and advanced toward Lord Hastings. "Are you the commander of this vessel?" he asked. Lord Hastings bowed. "I am," he replied. "Then I demand to know, as you claim, and appear, to be English, why you fired upon us?"