I'm writing a historical murder mystery where I explore how a small-time lawman motivated by a haunted past investigates a triple-murder close to home in the early high middle ages.

I'm feeling pretty good about my plotting, characters, and historical authenticity, but what I'm concerned about is creating a good mystery. I want the clues and themes to be subtle but identifiable and meaningful. Keeping the writing tight, with no deceitful or ham-handed misdirection is pretty important to me. I'm trying to aim for a story that's equally plot and character driven, if that matters.

I guess the best way to sum this question up is; how do you best make the questions you raise pay off in some way? How to ensure the main reveal is both unexpected but fair?

Any resources or tips are greatly appreciated.