"Trouble enough," replied the director. "Some hundred and thirty thousand dollars in gold is missing from the Mint!" "What!" Even Drummond was shaken out of his professional calm, not to mention his grouch. Robbery of the United States Treasury or one of the government Mints was a favorite dream with criminals, but--save for the memorable occasion when a gang was found trying to tunnel under Fifteenth Street in Washington--there had been no time when the scheme was more than visionary. "Are you certain? Isn't there any chance for a mistake?" The questions were perfunctory, rather than hopeful. "Unfortunately, not the least," continued Preston. "Somebody has made away with a hundred and thirty thousand dollars worth of the government's money. Seven hundred pounds of gold is missing and there isn't a trace to show how or where it went. The vault doors haven't been tampered with. The combination of the grille inside the vault is intact. Everything, apparently, is as it should be--but fifty bars of gold are missing." "And each bar," mused Drummond, "weighs--" "Fourteen pounds," cut in the superintendent. Drummond looked at him in surprise. "I beg your pardon," said Preston. "This is Mr. Bosbyshell, superintendent of the Mint. This thing has gotten on my nerves so that I didn't have the common decency to introduce you. Mr. Bosbyshell was with me when we discovered that the gold was missing." "When was that?" "Yesterday afternoon," replied the director. "Every now and then--at irregular intervals--we weigh all the gold in the Mint, to make sure that everything is as it should be. Nothing wrong was discovered until we reached Vault Six, but there fifty bars were missing. There wasn't any chance of error. The records showed precisely how much should have been there and the scales showed how much there was, to the fraction of an ounce. "But even if we had only counted the bars, instead of weighing each one separately, the theft would have been instantly discovered, for the vault contained exactly fifty bars less than it should have. It was then that I wired Washington and asked for assistance from the Secret Service." "Thus spoiling my vacation," muttered Drummond. "How many men know the combination to the vault door?" "Only two," replied the superintendent. "Cochrane, who is the official weigher, and myself. Cochrane is above suspicion. He's been here for the past thirty years and there hasn't been a single complaint against him in all that time." Drummond looked as if he would like to ask Preston if the same could be said for the superintendent, but he contented himself with listening as Bosbyshell continued: