The Innocence of Father Brown, by G. K. Chesterton

Chesterton was a contemporary of Arthur Conan Doyle, and Father Brown and Sherlock Holmes use similar methods, though their characters couldn't be  more different.  Father Brown is a Roman Catholic priest with keen observational skills and a deep understanding of human motivation.  In these stories, the first of the 51 written by Chesterton, Brown is found pitting his wits against Hercule Flambeau, an eventually redeemed thief (and murderer), and, Valentin, a famous detective (and murderer).