The Sherlock Holmes narrative is reflective of the classic detective story where the plot dominates. There is an intellectual satisfaction in finding clues, putting the data together and coming up with a solution. The reader is just as involved as the detective and there is always a closure to the mystery and the plot at the end; no loose ends. The mystery is stereotypical, the characters are never elaborated and are usually one dimensional.
In the medieval mystery, the plot is important, however not paramount to the outcome. The story is usually undercut by numerous sub-plots and sub-genres. For example in the medieval murder mystery in The Name of the Rose, the highlight is taken away from the murder by the sub-plot of the inquisition and the debate on heresy and the poverty of Christ. There is also the sub-plot of the love interest,the debauched nature of monastic life, the interest in the language and the forbidden knowledge.
So in the medieval mystery, the characterisation is very important. The solution is not what is driving the narrative. The other aspects of the novel are explored and elaborated on around the mystery. The mystery serves as a backdrop. In The Name of the Rose, the most important element is the search for truth and interpretation of universal truths and the murder mystery is actually left up to the reader; it is not even solved!
The Name of the Rose differs from other
mysteries" in that it contains numerous allusions that can be used to teach even a casual reader much about the Middle Ages. Take a couple of pages and simply Google the topics on those pages: relics, confession, scribes, symbolic animals. You will turn up some fascinating facts and beautiful illustrations of the medieval period. Because Eco was so knowledgeable about the period, his medievalism works--or if it doesn't work, Eco is making a point abouot dissimilarity.
The Name of the Rose is a story about a priest who is sent to investigate the serial deaths of other priests within the church. The killer is trying to hide the "true" religion of Jesus from the others. Those who get to close are killed.
In response to your question, depending on which story of Sherlock Holmes you are looking at..the answer could be the Christianity of religion vs. non-believers.
Check out the link below for more information about The Name of the Rose for background information that maybe able to help you further develop your paper.