“What is the significance of a letter found in a letter in the pocket of the book?”
To me the significance is that there is a story of a secret to be told. The letter is a blackmail letter from the sister of the second archdeacon, saying that she “knows what happened” and to pay her forty pounds. But this letter from what I can tell was never sent. It’s a look into the darkness of greedy, both financially and morally. The finacial aspect is wanting to be paid off for a secret that she has no proof of, which to me it hinted towards knowing there was a murder and by telling the secret people would be disgraced. The moral aspect is this is a church, a holy place where you are supposed to “love one another”, referring to the commandment, “Love thy neighbor”. The significance is also “God is always watching, or even “all you do you will be judged for”. Later on in the story we find the second archdeacon has suffered a similar fate as the first. Which can be interpreted as “practice what you preach” and “what you give is what you get”. Finally I believe the letter signifies that the truth has a way of coming out whether it is from someone’s words or a person’s reaction to the threat of those words.