"Mrs. Barcroft is A1, thanks," he replied. "At present she is engaged in keeping the home fires burning--with coal at fifty-five and six a ton, but I have not the faintest doubt that she will carry on to my utmost satisfaction. Well, cheerio, Entwistle! Glad to have met you again." The train moved off, leaving Entwistle to "carry on" in his particular line even as Barcroft Senior was "doing his bit" in a different sphere. Leaving the station, the Secret Service man made his way to the premises of Messrs. Grabnut & Plywrench. As he expected, a brief interview with the manager elicited the information that no cablegram had been sent by the firm to Holland. In fact, the Continental transactions of Messrs. Grabnut & Plywrench had ceased early in 1915. They had as much business in connection with Government contracts as they could possibly tackle. At sunset Entwistle returned to his post of observation on the city walls. Soon York, or as much of it as he could see from his lofty perch, was in darkness. He could hear the crowds in the main thoroughfares, the whirr of machinery in the workshops, the rumble of heavily laden trains, and the "chough-chough" of motor barges on the canal conveying raw material for the manufacturing centres of Yorkshire and the coast. It was a hive of industry working under cover of darkness. Cold work it was keeping the poverty-stricken tenement under observation. Occasionally people would pass along the narrow path on the walls. Entwistle would then lean on the lichen-grown parapet and feign a deep interest in the darkness until their footsteps died away; otherwise he hardly stirred during his prolonged vigil. "Great Peter" would have been tolling the hour of nine had it not been that the world was at war, when Entwistle heard a street door open. Straining his eyesight, he discerned a bent figure emerging stealthily from the house he was keeping under observation. "H'm!" he soliloquised. "A man with a military bearing ought never to trust to the disguise of decrepitude. Von Preussen, you've overreached yourself, I fancy." Keeping under the shelter of the breast-high parapet, Entwistle moved cautiously to the steps by the side of Bootham Bar. Gaining the roadway, he pressed against the side of the Gothic archway. For the present the thoroughfare was deserted. He could hear von Preussen's boots shuffling on the cobbles. Nearer, nearer... With a sudden spring Entwistle hurled himself upon the spy. The Secret Service agent had not mistaken his man. Almost before von Preussen knew what had happened he found himself lying face downwards on the pavement and his elbows being drawn together behind his back. "The game's up, Karl von Preussen," exclaimed Entwistle. "Yes," admitted the spy breathlessly. "You've scored this time. I'd like to know how you traced me." "You will in due course," replied Entwistle grimly, as he jerked his captive to his feet.