"All right," agreed Jerry. "Shake, Slim, just to show there's no hard feelings." "Won't do it," Slim muttered. "Oh, yes, you will," counseled Joe. "Shake hands, the two of you." Slim's good nature overcame his feigned reluctance, but as Jerry grasped his hand he gave Jerry a jerk that nearly took him off his feet. "Now we're square," said Slim, as Jerry rubbed his nearly dislocated shoulder. "Well, that pull _was_ a trifle heavy," muttered Jerry, determined to have the last word. "Now my plan is this," said Joe, facing the other two seriously. "The nearer we come to the zone of the German submarines, the more this man will try to arrange to notify them of our presence, and to do that he will have to use the wireless somehow. It seems likely that he would make his effort at night, because then it is easier for him to escape detection. "Now if we let Lieutenant Mackinson sleep during the day we could so divide up the work as for all of us to get some sleep, and then all could do watch at night. "The lieutenant could be in the wireless room, and one of us in the battery room, while the other two did duty outside. If one of us should hide under that stairway at the upper end of the passage, and the other in that alcove at the other end, no one could reach the wireless or battery rooms without our seeing. "It would be tiresome and monotonous work, all right, but it might accomplish the result." "I'm willing," said Jerry, "but you and I will have to do the outside work. Slim's a trifle heavy to get into either one of those hiding places." "Well, I'll cover the battery room," said Slim, ignoring Jerry's remark. "Let's see Lieutenant Mackinson, then," suggested Joe, and they went to find the young officer who was convalescing from his encounter with the spy. When he had approved the plan they got the O. K. of the captain. And so it was, four hours later, with the lieutenant in the wireless room, and Slim in the battery room adjoining, and Joe and Jerry stowed away in the hiding places selected, their long night vigil began. Hour after hour dragged itself by without a development, the intense silence broken only by the sounds of the engines and the wash of the sea against the ship. To the three boys, unable to see or talk to each other, and Joe and Jerry scarcely daring to move, the minutes lagged like hours, and the hours like dull, black, endless nights. Dawn came, and with it new activities in all parts of the vessel, but without a reward for their watch, and as the two lads crawled from their places of concealment at either end of the passage, to join Slim and Lieutenant Mackinson, there were mutual feelings of disappointment, but none of weakened determination. "What luck?" asked the captain, coming in at that moment. "None, sir, at all," the lieutenant responded.