“It is no concern of ours,” replied Thorndyke. “We’ve got the pearls, and that finishes the business. There will be no more shadowing, in any case.” Miss Bonney heaved a comfortable little sigh and glanced gratefully at Thorndyke. “You can have no idea what a relief that is!” she exclaimed; “to say nothing of the treasure-trove.” We waited some time, but as neither the fugitives nor the constables reappeared, we presently made our way back down Brownlow Street. And there it was that Brodribb had an inspiration. “I’ll tell you what,” said he. “I will just pop these things in my strong-room--they will be perfectly safe there until the bank opens to-morrow--and then we’ll go and have a nice little dinner. I’ll pay the piper.” “Indeed you won’t!” exclaimed Miss Bonney. “This is my thanksgiving festival, and the benevolent wizard shall be the guest of the evening.” “Very well, my dear,” agreed Brodribb. “I will pay and charge it to the estate. But I stipulate that the benevolent wizard shall tell us exactly what the oracle said. That is essential to the preservation of my sanity.” “You shall have his _ipsissima verba_,” Thorndyke promised; and the resolution was carried, _nem. con._ An hour and a half later we were seated around a table in a private room of a café to which Mr. Brodribb had conducted us. I may not divulge its whereabouts, though I may, perhaps, hint that we approached it by way of Wardour Street. At any rate, we had dined, even to the fulfilment of Brodribb’s ideal, and coffee and liqueurs furnished a sort of gastronomic doxology. Brodribb had lighted a cigar and Thorndyke had produced a vicious-looking little black cheroot, which he regarded fondly and then returned to its abiding-place as unsuited to the present company. “Now,” said Brodribb, watching Thorndyke fill his pipe (as understudy of the cheroot aforesaid), “we are waiting to hear the words of the oracle.” “You shall hear them,” Thorndyke replied. “There were only five of them. But first, there are certain introductory matters to be disposed of. The solution of this problem is based on two well-known physical facts, one metallurgical and the other optical.” “Ha!” said Brodribb. “But you must temper the wind to the shorn lamb, you know, Thorndyke. Miss Bonney and I are not scientists.” “I will put the matter quite simply, but you must have the facts. The first relates to the properties of malleable metals--excepting iron and steel--and especially of copper and its alloys. If a plate of such metal or alloy--say, bronze, for instance--is made red-hot and quenched in water, it becomes quite soft and flexible--the reverse of what happens in the case of iron. Now, if such a plate of softened metal be placed on a steel anvil and hammered, it becomes extremely hard and brittle.” “I follow that,” said Brodribb.