He proved a good tenant, none better. He came as regularly as the morning and went as regularly. His presence in the house was quite unknown to the gentleman who occupied the top floor, and who had long congratulated himself on his luck in having a lodging over which he had such absolute control. As a matter of fact there was only one entrance to his upper floor, save that on the street. A rude little staircase ran up from the kitchen into a tiny square hall, and a door opened into the room which had been Mikey's. It was by this door that every afternoon, when Katie came home from Dick's, she went upstairs to make the rooms. Max's habits were very regular--exemplary person that he was. He was at the munition works at seven and never left until five. His doors were carefully locked behind him. He had no need to concern himself about anything in Katie Flaherty's house. But in this secure dwelling, strange things were going on in those hours when Max was at his laboratory and Katie at the rectory. Every morning, promptly at 8:30, a quiet, tired looking young engineer unlocked the side door of Katie Flaherty's house, and drew his curtains. But once the curtains were drawn, an extraordinary transformation took place. The fatigued face became relaxed, the heavy, dirty boots were replaced by the softest of slippers; two very dangerous looking weapons were slipped into his belt; and in the big pockets of his soft sack coat something that looked like a pair of handcuffs. And then, with keys in hand, he quietly slipped up the back stairs, opened this door and began an investigation of the belongings of Mr. Max Dalberg, Reuben Cowder's "wonder of the laboratory." And the things that he found! You could tell that by the glint of victory in his eye, by the moments when he would straighten himself and address the air in a whisper, "Could you beat it?" When he would noiselessly tap his thigh and say, "It's the completest thing I ever heard of." The young man was making out a pretty case in Max's secure chamber, little by little, from the papers and photographs which he examined with such scrupulous care day by day, always leaving them exactly as he found them, taking infinite pains not to leave behind him any trace which might make Max suspicious that his privacy had been invaded, and he gathered the proofs of as fine a piece of destructiveness as any planned within the borders of the United States by the band of plotters that Germany had sent out. What young Mr. Barker found was simply this--a carefully laid scheme, every detail worked out with German efficiency, to blow up simultaneously every munition plant in that great district around Sabinsport, where now literally millions of dollars' worth of shells and shrapnel and wires and guns were being made for the Allies.