Jarvis, the narrator of this novel, is a doctor who is currently lacking money, a proper job and a place to live. By chance he meets Thorndyke, an old frend from his university-times. Thorndyke is a lecturer but also a medio-legal consultant who (at least in this book) is employed by the defense to prove somebody's innocence. Thorndyke offers Jarvis a job as his assistant (and even a place to stay)Now parts of this do sound vagelue familiar...if only I knew where I read something like this before.OK, even though I don't like these direct comparisons between books, I think it does make sense here to point out the differences and similarities between Thorndyke and Holmes.Both Thorndyke and Jarvis have studied medicine, so it's different to Holmes where Watson has at least his medical on him. Nevertheless Jarvis still had quite an active part in the investigation. Thorndyke sends him out to talk to some whitnesses (and unlike Holmes, he doesn't chuckle afterwards and point out that he actually missed all the important bits but it doesn't matter as he already got all the information he needed, quite the contrary: when Jarvis wonders if he is helping in any way to solve the case, Thorndyke insures him that his contribution is very valuable).There is even quite a massive Take That towards Holmes: in one scene Thorndyke looks out of the window, spots a man and, based on his clothes, posture and movements, makes an assumption to what this man's job is, while stressing that this is just a guess that could in fact be wrong and that people who claim that they can tell for sure only exist in "this romantic detective fiction" (awwww...so this kind of bitching around has existed for a long time...I always thought that it only started with policemen in novels complaining about policemen on TV shoting people all the time without facing any consequences).Generally speaking you could probably say that Holmes is a genius, while Thorndyke is just a very talented and intelligent man. Thorndyke seems more human and you can't imagine him not to know that the earth revolves around the sun. At the same time, Jarvis seems less awe-struck by Thorndyke than Watson is by Holmes. Of course Jarvis is also very impressed, but overall it seems like he simply accepts that Thorndyke is brighter than himself.(I just notice that currently I sound like somebody who can't stand Holmes and Watson. Let me assure that this is not true. I love them and all their quirks and habits, I'm just trying to point out the differences here).The major difference is of course that Thorndyke is a forensic detective. That means basically that where Holmes says "Oh I once wrote an article about distinguishing different types of tobacco-ash and so I know that this ash comes from brand X" Thorndyke goes into detailed explanations on the How-tos of forensic science (in this books it's on fingerprinting) and we do get several pages of description of how he investigates, photographs and enlarges a fingerprint. If you are a normal human being that might bore you a bit...if you are like me and one of your most-loved posessions is a series of books about the advantages forensic science made from the 1850s onwards you will squee excessively and ask yourself why you never heard of these books before.Another thing that is a bit unusual at first is that, as I already wrote, in this book Thorndyke works for the defence, meaning he has to prove somebody's innocence, not finding out who was guilty.Overall I can understand why Holmes has stayed so popular and Thorndyke is nearly forgotten. He caters more for a niche-audience ;) But if you're, like me, part of that niche, The Red Thumb Mark is well worth a try.