Nick forced it down and discovered the opening of a tube through the wall, and in the tube a cylinder such as Patsy had seen in the subterranean chamber. Nick instantly hit upon the truth, of course, and the mystery as to how the merchandise had been taken from the store ended then and there. “A pneumatic tube,” he said to himself, noting the tight-fitting flange of felt around the end of the cylinder. “Similar to those of a cash system. The tube evidently runs underground to another building, where there must be an engine and air pump for removing the air from the tube. That done, and this plate lowered, the cylinder would fly through the tube in an instant.” Nick carefully noted the probable direction of the tube, then turned a knob in the metal end of the cylinder, from which he took, as he expected--the bundle seen under Lombard’s arm only ten minutes before. Nick closed the tube and panel, then took the bundle up to Mr. Mantell’s private office, where he found both father and son. “By gracious, Nick, there has been another theft,” Frank Mantell cried, when the detective entered. “A pair of costly lace curtains is missing from that department.” Nick did not care for any particulars. He sat down in one of the large leather chairs and placed the bundle on the floor behind it. “That’s too bad, Mantell,” he remarked. “I would like to question one of your managers. Send for Mr. Lombard, since we happened to notice him a few minutes ago.” Frank Mantell looked surprised, but hastened to obey. Lombard entered in about five minutes, apparently apprehending nothing. Nick had removed his disguise and thrust it into his pocket. “Sit down, Mr. Lombard,” said he, without waiting to be introduced. “I am told there has just been another mysterious theft in this store.” “Yes, so I have heard,” was the quick reply. “I was just going to look into the matter.” “Don’t you think it would be more profitable to look into that pneumatic tube that leads out of the receiving room?” Nick inquired. Lombard turned as white as his shirt front. “I don’t know what you mean,” he faltered. “What--what tube?” “That in which I found this bundle a few minutes ago,” said Nick, taking it from behind his chair and tearing it open. “Here are the stolen lace curtains. I refer to the tube, Mr. Lombard, in which you placed them.” Lombard started to rise, but his knees gave way under him and he nearly fainted in his chair, while Mantell and his father stared in speechless amazement. Nick leaned forward, and, before Lombard fairly knew it, snapped a pair of handcuffs on the culprit’s wrists. “Now,” said he, more sternly, “tell me where that tube leads, Mr. Lombard, and be quick about it. The jig is up for you and your confederates.” Lombard pulled himself together and glared at Nick with a scowl. “You’ll learn nothing from me,” he growled bitterly. “Find out for yourself, if you want to know.”