"Correct logic? Yes. Of course I admit nothing as to facts."
"Either or both of these robberies are secondary to the murder. That I have determined to unravel if I can. At present I think the train robber and the murderer was one and the same person. Now, there is one clue which I have not been able to follow, but which, if pursued, I am certain will lead me straight to the criminal."
"And that is?"
"The button which I found in the room. That is significant. It is too great a coincidence that it should match your set, not to have an explanation that would shed light upon this case."
"How do you expect me to assist you in that direction?"
"As long as I thought you guilty, I believed that you had lied when you said that the seventh button of the set was the Shakespeare pin which your wife had. That is why I thought it of importance to recover it; sufficiently so, to send my spy, Lucette, into the house with instructions to obtain it if possible. Now that I believe you innocent of the murder, this thought has recently come to me. When I first told you about this button, before you would speak about it, you asked me to allow you to examine it. After doing so, you gave it back to me, with a cheerful smile. If that button had been evidence against you, I see now that it would have required a powerful nerve to appear so unconcerned, and especially to return it to me. The question then that I wish you to answer is, what was it that you saw on that button, which satisfied you that it was not of your set?"
"In the first place, Mr. Barnes, I knew that there were but three like it, the other three having different heads, and the seventh being the Shakespeare button. Thus as I knew that all the buttons were in my possession, I felt safe."
"But in the second place," said the detective, "there was a distinct difference between the buttons, and by that you were even more assured. Am I not right?"
"Mr. Barnes, you deserve to succeed, and I hope you will. I will aid you all that I can. You are right. There is a difference in the buttons. Have you yours with you?"