"All of a sudden I was grasped by the neck and one arm from behind, and thrown into that closet. Before I could utter a word I was a prisoner behind a locked door. I called several times, and, receiving no response, realized that I must be some distance from anyone else and that the noises of the engines completely drowned out my voice. "Every moment it became more stifling in there, and I had no doubt that I had walked directly into a death-trap. It was then I began signaling on the steam-pipe. I guess it was a mighty lucky thing for me that Slim Goodwin strolled out on deck just at the time he did." And that was all that Lieutenant Mackinson could tell. The mysterious stranger remained what he had been from the first--a desperate and dangerous and unknown spy, lurking somewhere upon the American transport _Everett_ with the evident intention of making the ship's position known to German U-boats when the _Everett_ and her convoy of cruisers and destroyers entered the danger zone. Then it was, with the lieutenant temporarily disabled as a result of his experience, that the three boys from Brighton, who seemed somehow to have been selected by Fate as the despoilers of all the spy's plans, put their heads together to devise a scheme of capture. "We've got more than one good reason for wanting to get this fellow," Slim reminded the others with considerable warmth, during the course of their deliberations. "First and foremost, of course, is our plain duty to our country, to which he is an enemy and a traitor. "But, in addition to that, there is that knockout that he handed to Joe, and the midnight scare he gave Jerry and me, and finally his effort to kill Lieutenant Mackinson by slow suffocation, not to mention the nerve of the fellow in coming back the way he has." "Yes," added Jerry, "we owe him a lot, and it is up to us to figure out how we can square the debt." "Well," said Joe, "I think I've got a plan that will work; but we've got to remember that we are dealing with a very shrewd man." "Well, what's your suggestion?" Slim demanded. "That we divide our forces," answered Joe solemnly, "lie in wait and try to ambush the foe." "Right!" cried Jerry. "Joe, you'll be a general before this war's over." "Along what lines do we disperse our forces, General?" asked Slim. "Along what lines would His Royal Stoutness suggest?" demanded Jerry. "Oh, you don't have to keep reminding me that I'm a trifle heavy," Slim replied in a peevish tone. "A trifle heavy! Get that, will you," echoed Jerry with a gale of laughter. "A trifle heavy! Oh, my!" "You'll find out if I sit on you," Slim threatened, in a belligerent tone. "Come now," said Joe, "this isn't making any progress toward capturing the spy." "No," Jerry responded, "and that's our first duty, even if it is a trifle heavy." "I've warned you," Slim snapped out. "Quit it now," ordered Joe. "Let's get down to serious business."