The Red Thumb Mark

The mysterious fiction, The Red Thumb Imprint, describes the story of the valuable diamonds that are missing, and the thumbprint of Reuben Hornby is found in a drop of blood on a piece of paper at the lower part of the safe. The specialists of Scotland Yard are all in agreement. Apparently, this is an obvious situation. Or, on the other hand, is it? For reasons known exclusively to himself, Dr. John Thorndyke feels a little unsure about the authenticity and starting origins of the evidence....