“Now, of this there could be only one reasonable explanation. Disregarding the fact that no one would screw the suspension plates on a frame without ascertaining which was the right way up, and assuming it to be hung up inverted, it was impossible that the misplacement could have been overlooked by Jeffrey. He was not blind, though his sight was defective. The frame was thirty inches long and the individual characters nearly an inch in length⁠—about the size of the D 18 letters of Snellen’s test-types, which can be read by a person of ordinary sight at a distance of fifty-five feet. There was, I repeat, only one reasonable explanation; which was that the person who had inhabited those chambers was not Jeffrey Blackmore.