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.