From the point where I watched I could see that the old man with considerable gesticulation was standing upon the shore facing seaward and explaining something to his companion. The Belgian apparently put many questions to him, and had become intensely interested. Then presently his companion produced a paper from his pocket--evidently a plan, for he pointed out something upon it. They both lit their pipes, and sitting down upon a rock discussed something quietly. Apparently Busch was making an elaborate explanation, now and then pointing with his finger seaward. Where he pointed was the channel through which passed all the shipping into the Humber. Then, after a time, he rose from where he sat, and seemed to be measuring a distance by taking paces, his companion walking at his side over the level expanse of sand. Suddenly he halted, pointing to the ground. Dubois examined the shore at that point with apparent curiosity. With what object I could not imagine. They remained there for fully an hour, and the sun had already set when they returned to Patrington, and took the train back to Hull. That old Busch was a spy I had proved long ago, but what part Dubois and Gessner were playing was not yet at all clear. On the following evening, about ten o'clock, I saw Dubois near the Dock office, and on watching him, followed him to the factory, which he entered with his key. Beyond the gate was the small paved courtyard in which rose the high chimney. Within the factory he lit the gas, for I could see its reflection, though from the street I could not get sight of the lower windows. The night was bright and moonlit, and as I waited I heard within the grinding of a windlass, and saw to my surprise, a thin light iron rod about six feet long and placed vertically rising slowly up the side of the chimney stack, evidently being drawn up to a pulley at its summit. Dubois was hoisting it to the top, where at last it remained stationary, its ends just protruding beneath the coping and hardly visible. Scarcely had this been done when Busch came along, and I had to exercise a quick movement to avoid detection. He was admitted by Dubois, and the door was closed and locked as usual. I stood beneath the wall, trying to overhear their words. But I could understand nothing. Suddenly a dull, crackling noise broke the silence of the night, as though the sound was dulled by a padded room. Again I listened. Then at last the truth dawned upon me. The spies had put in a secret installation of wireless telegraphy! Those intermittent sounds were that of the Morse code. They were exchanging signals with some other persons. Gessner was absent. No doubt the corresponding station was at that house high upon Sydenham Hill to the south of London, two hundred miles distant!