"I haven't finished yet," said Quarles, interrupting me. "Obviously one man couldn't remove all that gold and get it away from the city that night. The robber, with the duplicate keys he had in his possession, could go to that strong-room when he liked; all he had to do was to take the precaution that he was not seen. A very few visits sufficed, no doubt; but on each occasion he brought away some spoil with him, which he concealed, I imagine, somewhere in the bank, where he could easily get at it. The robbery extended over a period of time, that is my point, and whether dummy bags were substituted for those taken, or a bag was gradually emptied, does not matter." "But, my dear professor, your ingenious theory overlooks the fact that, if it were true, there would be no use for the final catastrophe--for attacking the porter and blowing up the strong-room." "Ah! that brings me to the mental attitude of the thief. I think we shall find that an inspection of those strong-rooms was imminent, and the thief was anxious, first, to make a last addition to his store, and, secondly, to suggest the work of a gang, and so minimize all risk to himself. Besides----" The professor paused. There was a knock at the door, and the servant brought in a telegram. Quarles opened it and read it. "Besides, one has to consider the mental twist a man may have," he went on. "We shall probably find in this case that at the back of the robbery was an awful dread of the future, of the helplessness and poverty that might come into it, an abnormal morbidness which so constantly drives men to strange actions." "But how could Ewing manage to conceal himself in the bank, or get into it even? Everybody knew him, everybody probably knew of his dismissal." "How about the window in the roof?" said Quarles, handing me the telegram, and I read: "Left early this afternoon; returned home." "That refers to the general manager, Mr. Wickstead," said Quarles. "Probably he does not intend to remain at home, but we may catch him there. I have a man watching him. I thought my statement that we had traced Ewing would frighten him. He is the thief, Wigan. He is also the friend Ewing spoke about to Ursula Yerbury. Don't you see the cleverness? He helped Ewing out of the country, after frightening him by saying that a prosecution had been decided upon; sent him somewhere where he was not likely to hear of the robbery, and tried to throw dust in our eyes by expressing pity for him and a belief in his innocence." "If you are right, what a villain!" I exclaimed. "An abnormal dread of the future, Wigan; I think we shall find that is at the bottom of it, and we shall probably find also that the whole of the spoil is intact. The law, of course, cannot enter into these curious mental attitudes. Come! I think we shall provide a sensation for the world of finance."