"The Moving Finger writes; and, having writ, moves on"
Rubaiyat (Fitzgerald translation)
Confession: For the longest time, I'd mix up Freeman Wills Crofts and R. Austin Freeman.
Life after medical school has not been the success story Jarvis had hoped it to be. One day, he runs into his old friend John Thorndyke, who unlike him has made a bit of a name for himself as a medical expert in the field of legal problems. Jarvis is invited for dinner, but the friend's reunion is disturbed by Reuben Hornby and his lawyer, who look for Dr. Thorndyke's help. Diamonds kept in the safe of Reuben's uncle's safe have been stolen, and the one single clue left on the scene of the crime is a bloody thumb mark found on a piece of paper lying inside the safe, which was obviously not there when the diamonds were last seen. The thumb mark is that of Reuben, but he swears he has nothing to do with it. Thorndyke's interests are piqued, and he decides to hire his old friend Jarvis as an assistant while they do their own scientific investigation into what the police considers an open-and-shut case in R. Austin Freeman's The Red Thumb Mark (1907).
The infamous "zoom and enhance" scene we nowadays see in crime TV dramas is of course a bit silly (blowing up a photograph is not magically going to enhance its resolution), but it is a good example of how much science and technology has become a part of our world, and particularly, crime and mystery fiction. I'd guess that many people had of course heard of forensic techniques like DNA testing, tests for blood spatters and more, but obviously series like CSI helped inform the average viewer of what technology can do when fighting crime. Of course, science and technology has always been an important factor of mystery fiction. A mystery is solved by combining clues, and clues most often consist of tangible clues that can be obtained through an application of the sciences. Our first meeting with a certain Mr. Sherlock Holmes for example had him discover a new reliable test for blood stains, which he assures Dr. Watson and the reader would be the most practical discovery for the medico-legal world. But even something as simple as using plaster of Paris to preserve a footprint is an application of science.
So that we'd eventually get a detective who'd specialize completely in utilizing science and technology to solve crimes was not a surprise. R. Austin Freeman's Dr. Thorndyke is most often seen as the quintessential detective who champions the use of science in crime-fighting, and The Red Thumb Mark is in fact the very first novel in the Dr. Thorndyke series. I think I have read only one Dr. Thorndyke novel in a longaway past (The Eye of Osiris) and to be honest, I remember awfully little of that book, so perhaps it was good that I resumed my Thorndyke reading with the book that introduced the world to the scientific investigator.
In a way, I'd say that The Red Thumb Mark is almost more like a case-study than a mystery story. That is not fair to the novel perhaps and it's obviously a story of fiction (with some melodrama, even), but if you look at the core mystery plot, one could argue that the story's focus lies almost solely on the titular thumb mark, and by extension, the issue of fingerprints in general and their use in criminal investigation. Upon taking the case, Dr. Thorndyke devotes his time on examining the one damning clue in the whole case in an attempt to save Reuben. In the course of the story, Dr. Thorndyke will explain certain characteristics of fingerprints that show how they are not, like was thought back in the time, that fingerprints were the one-and-all clue. It is here where you do really feel that time has passed by a lot since The Red Thumb Mark was first published, because Dr. Thorndyke's might've been surprising back then to the reader, but the plot as is has troubles really standing out to a modern reader, as the caveats pointed out by Dr. Thorndyke are common knowledge now, and almost warrant for a shrug. In fact, I think the 'surprise' wore off pretty quick, as Edogawa Rampo also wrote a (translated) short story based on a similar idea (focusing on fingerprints), and there I think it worked better as the device was not meant to sustain a novel-length story, but just a short story.
When I say The Red Thumb Mark reminds me of a case-study, it's because it is basically looking at the practical uses of a certain topic (in this case fingerprints), with the story mostly serving as device to make it easier to swallow. There is of the course the mystery of how Dr. Thorndyke is going to solve Reuben is innocent, and there is even a courtroom drama segment as the finale, but "other stuff" like who the real culprit is, are only of secondary importance to the plot, and the real aim of this story is closer to "You may have heard of fingerprints as an important development in criminal investigation, but there are some caveats to that." While reading The Red Thumb Mark, I also had to think of Melville Davisson Post's Randolph Mason series, which basically presented case-study-esque stories based on rather silly US laws, but I think those stories worked better because of the more surprising settings. The Red Thumb Mark in comparison feels more dated, as we, as in the "average reader", have learnt so much more about things like fingerprints.
All in all, I thought The Red Thumb Mark had an okay-ish idea, but it does feel dated because it devotes all its energy at looking at one particular topic that has since grown less surprising. This is of course not the fault of the book itself, but it does mean that a modern reader has more trouble to genuinely admire the tale. I also can't shake away the feeling this novel feels more like a thought experiment focusing on fingerprints, despite the surrounding story and melodrama.