It occurred to the store detective that if the Englishman was rude to Mr. Boon it was altogether likely the duke treated his private secretary as a servant. It gave the detective pleasure to imagine this, for whenever the colonel had looked at Mr. Donnelly it was with the casual indifference with which men look at chairs or cobblestones. This made T. Donnelly feel that he was not alive, and he disliked the aristocratic undertaker. The motor turned into Fifth Avenue, sped northward, and halted before a house. Mr. Boon recognized Mr. Walton's residence. The colonel alighted quickly and said “Come with me!” in the tone foreigners use to menials, and didn't even turn his head to see if he was followed, but walked up to the door and rang the bell. A man in livery opened the door. “I am Colonel Lowther!” “Yes, sir. His Royal Highness said you were to wait in the drawing-room unless there was somebody with you; in which case you were to be taken to him, sir.” “Come on!” said the colonel to Mr. Boon and the private policeman. The footman preceded them to a door at the back of the foyer hall, opened it, drew back heavy portières, and announced, solemnly: “Colonel Lowther!” The colonel entered. So did Mr. Boon and Donnelly. A man stood gazing out of a window. His back was toward them. For the first time Mr. Boon--so he said later--felt that something was wrong. Yet he made no effort to protect himself. “Your Highness, here are the pearls.” The duke turned round. He had a kindly face, had white hair and mustaches. “Let me have them!” said his Royal Highness, in the husky whisper of a man suffering from acute laryngitis or partial paralysis of the vocal cords. “I know that voice!” shouted Donnelly, and the jeweler knew he might fear the worst; but, before they could put their hands in their pockets for their revolvers, strong fingers took strangle-holds on their throats, a spray of ammonia had been squirted into their nostrils and eyes, and they were helpless. In a jiffy their wrists were handcuffed behind their backs, their feet were fastened with leg-irons, their mouths pried open with a bowie-knife blade that made them cease struggling. Pear-gags were inserted into their mouths. Donnelly squirmed and carried on like a frightened child--but at the same time kept unfrightened eyes on the duke. Not so Boon, who was as pale as ivory. The duke turned his back on his captives and put on a black cloth mask, but the watchful Donnelly noticed that he put into his pocket what looked like false mustaches. He also donned a pair of black gloves, but not before the policeman had seen a long, white scar, beginning at the knuckles and disappearing up the wrist into the cuff. Donnelly recalled having heard or read a description of a professional crook that tallied with what he had seen. It would make the work of capture easier. The masked duke picked up the precious valise and said, “Take them to the others.”