Then Mrs.Hornby had a brilliant idea.

She suddenly remembered the 'Thumbograph,' and thinking to set the question at rest once for all, fetched the little book and showed it to the detective.

It contained the prints of both thumbs of Mr.Reuben (among others), and, as the detective had with him a photograph of the incriminating mark, the comparison was made then and there; and you may imagine Mrs.Hornby's horror and amazement when it was made clear that the print of her nephew Reuben's left thumb corresponded in every particular with the thumb-print that was found in the safe.
"At this juncture Mr.Hornby arrived on the scene and was, of course, overwhelmed with consternation at the turn events had taken.

He would have liked to let the matter drop and make good the loss of the diamonds out of his own funds, but, as that would have amounted practically to compounding a felony, he had no choice but to prosecute.

As a result, a warrant was issued for the arrest of Mr.Reuben, and was executed this morning, and my client was taken forthwith to Bow Street and charged with the robbery." "Was any evidence taken ?" asked Thorndyke.
"No.