"Then did Corbett travel by the same mail as this letter in order to murder Lady Dyke? It is dated October 15th, and she was killed November 6th. It takes twelve days, at the quickest, for a letter to come here from Wyoming. And Corbett, the writer of it, not the receiver, must have travelled in the same steamer, or its immediate successor." Mr. White's face fell, but he stuck to his point: "Anyhow, Corbett was here about that time. I have seen the secretary to the company that owns these flats. Corbett took the rooms for six months from September first. When asked for references he gave his sister's name, and as she banks with the National--and she has always paid her rent for five years--it was good enough. Still, I must confess that Corbett could hardly be in Wyoming in October if he lived here in September and in November." The barrister answered between his set teeth: "Yes, it is rather puzzling." "Perhaps the letter was left there as a plant." "An elaborate one. It must have been conceived a month before the murder." "But suppose it never came from Wyoming. We have no proof that it was written in America." "We have proof of nothing at present." "Well, Mr. Bruce, have you a theory? This is the place where you ought to shine, you know." "I have no theory. I must think for hours, for days, before I see my way clear." "Clear to what, sir." "To telling you how, when, and where to arrest the murderer of Lady Dyke." "So this find of mine is of great importance?" "Undoubtedly. I remember its contents sufficiently, but you will let me see it again if necessary?" "With pleasure, sir. And that reminds me. You never returned that small bit of iron to me. You recollect I lent it to you some time since." "Perfectly. Come with me. I will model it in wax and give it to you." "All right, sir; but as we are here I may as well continue my search. I may drop on something else of value." Bruce resumed his seat, and did not stir until the detective had completely rummaged the cabinet. The reading of that queer epistle from Corbett to "Bertie"--from the real Simon Pure to the sham one--from one man to his double--had stopped him at the very threshold of disclosure. The document impressed him as being genuine. If so, who on earth was Corbett, and why had Mensmore taken his name, if that was the solution of the tangle? Whatever the explanation, he would not jump to a conclusion. The web had closed too securely round Mensmore to allow of escape. Hence, Bruce could bide his time. Another week might solve many elements in the case now indistinct and nebulous. He would wait. The detective finally satisfied himself there was nothing else in the cabinet. He approached the fireplace, peered into every vase on the over-mantel, picked with his penknife at the back of the frame to feel for other letters, and in doing so several times kicked the fender.