I am a huge fan of the Sherlock Holmes stories by Sir Arthur Conan Doyle, particularly in the form of audiobooks. A special hobby of mine is to listen to the first half of an audiobook, then to pause it and to draw my own conclusions before listening to the rest. Following this habit, I discovered a very interesting peculiarity in The Valley of Fear today.
The full story can be found here:
The Occurrences
In The Valley of Fear, Sherlock receives an encrypted message from a certain Fred Porlock. According to Sherlock, Porlock is one of his informants, who pretends to be a follower of Professor Moriarty – Sherlock’s archenemy. The message contains the following information:
534 C2 13 127 36 31 4 17 21 41 DOUGLAS 109 293 5 37 BIRLSTONE 26 BIRLSTONE 9 47 171
Sherlock quickly deduces that the numbers must correspond to certain words in a book. 534 is the page number, C2 the column number (second column) and the numbers that follow are the word numbers on the page (the 13th word, the 127th word, etc.). The words “Douglas” and “Birlstone” are not encrypted, Sherlock assumes, since they could not be found in the book that was used. He further assumes that he will soon receive a second letter from Porlock containing the book or at least the name of the book that is needed to decipher the message. This would prevent anyone (including Professor Moriarty) from being able to decipher the message without intercepting both letters. Indeed, Sherlock soon receives a second letter, but he is disappointed. The second letter reads:
Dear Mr. Holmes
I will go no further in this matter. It is too dangerous –he [by he Porlock means Professor Moriarty] suspects me. I can see that he suspects me. He came to me quite unexpectedly after I had actually addressed this envelope with the intention of sending you the key to the cipher. I was able to cover it up. If he had seen it, it would have gone hard with me. But I read suspicion in his eyes. Please burn the cipher message, which can now be of no use to you.
– Fred Porlock.
Nevertheless, using just his acumen, the great Sherlock is able to find the required book (his train of thought is given in The Valley of Fear) and to decipher the message. It reads:
There is danger may come very soon one Douglas rich country now at Birlstone House Birlstone confidence is pressing.
Sherlock’s interpretation of the message is the following:
When you search a single column for words with which to express your meaning, you can hardly expect to get everything you want. You are bound to leave something to the intelligence of your correspondent. The purport is perfectly clear. Some deviltry is intended against one Douglas, whoever he may be, residing as stated, a rich country gentleman. He is sure – ‘confidence’ was as near as he could get to ‘confident’ – that it is pressing. There is our result – and a very workmanlike little bit of analysis it was!
Soon enough, Sherlock is informed that a certain gentleman named Douglas was murdered in Birlstone. The case is launched and Sherlock quickly sets off for Birlstone. This is where I paused the audiobook (earlier than usual – I was interrupted).
The Deduction
After pondering about the aforementioned occurrences for a while, I think the case is perfectly clear: Sherlock is running into an ambush. And, since he is the greatest detective of all times, he’s probably even well aware of it.
The reasoning is the following: The encryption of the first message is utterly useless. Let’s assume that Professor Moriarty is somehow able to intercept the message. He reads the words “Douglas” and “Birlstone” and sees that Sherlock is the recipient of the letter. Now, Moriarty is a brilliant head, on par with Sherlock. How long will it take him to deduce that the purpose of this letter is to inform Sherlock about the planned murder on Mr. Douglas in Birlstone and that Fred Porlock is not in fact his follower but a spy? Less than a split second. He would have Porlock killed immediately (before maybe making fun of his stupidity).
It does not seem likely that Fred Porlock is that careless and dumb. In addition, why would he write the long second letter that gives away his whole role (and this letter is not even encrypted!), instead of just sending the name of the book? Doesn’t make sense either.
Therefore, the best explanation is that the whole thing is an ambush. Fred Porlock is a double spy (maybe he doesn’t even exist at all and was simply invented by Professor Moriarty) and the message is sent to Sherlock to attract his attention. This is done with the nice little deciphering puzzle. And Professor Moriarty left the words “Douglas” and “Birlstone” unencrypted, since he wanted to make sure that Sherlock will take the case and go to Birlstone, even if he is not able to decipher the message as a whole.
Elementary, my dear Watson!
I’m very curious to hear the rest of the story now. Maybe I will write a second post about whether my deductions were actually right or not.
P.S.: I took the featured image of this post in the Sherlock Holmes museum in Meiringen, Switzerland. An amazing place, I can highly recommend going there!