"Where are the gold bars?" asked the detective. "The place looks like it had been well looted." "They were all taken out this morning, to be carefully weighed," was Preston's reply. "I'd like to see some of them stacked up there along the side of the grille, if it isn't too much trouble." "Surely," said Bosbyshell. "I'll have the men bring them in at once." As soon as the superintendent had left the room, Drummond requested that the door of the grille be placed in its usual position, and Cochrane set it up level with the floor, leaning against the supports at the side. "Is that the way it always stays?" inquired the Secret Service man. "No, sir, but it's pretty heavy to handle, and I thought you just wanted to get a general idea of things." "I'd like to see it in place, if you don't mind. Here, I'll help you with it--but we better slip our coats off, for it looks like a man's-sized job," and he removed his coat as he spoke. After Cochrane had followed his example, the two of them hung the heavy door from its hinges and stepped back to get the effect. But Drummond's eyes were fixed, not upon the entrance to the grille, but on the middle of Cochrane's back, and, when the opportunity offered an instant later, he shifted his gaze to the waist of the elder man's trousers. Something that he saw there caused the shadow of a smile to flit across his face. "Thanks," he said. "That will do nicely," and he made a quick gesture to Preston that he would like to have Cochrane leave the vault. "Very much obliged, Mr. Cochrane," said the director. "We won't bother you any more. You might ask those men to hurry in with the bars, if you will." And the weigher, pausing only to secure his coat, left the vault. "Why all the stage setting?" inquired Preston. "You don't suspect...." "I don't suspect a thing," Drummond smiled, searching for his own coat, "beyond the fact that the solution to the mystery is so simple as to be almost absurd. By the way, have you noticed those scratches on the bars of the grille, about four feet from the floor?" "No, I hadn't," admitted the director. "But what of them? These vaults aren't new, you know, and I dare say you'd find similar marks on the grille bars in any of the others." "I hope not," Drummond replied, grimly, "for that would almost certainly mean a shortage of gold in other sections of the Mint. Incidentally, has all the rest of the gold been weighed?" "Every ounce of it." "Nothing missing?" "Outside of the seven hundred pounds from this vault, not a particle." "Good--then I'll be willing to lay a small wager that you can't find the duplicates of these scratches anywhere else in the Mint." And Drummond smiled at the director's perplexity. When the men arrived with a truck loaded with gold bars, they stacked them--at the superintendent's direction--along the side of the grille nearest the vault entrance. "Is that the way they are usually arranged?" inquired Drummond.