G. K. Chesterton 
The Secret of Father Brown 

Father Brown returns in his fourth collection of stories, and his sidekick Flambeau makes a return as well, although only in the two framing stories at the beginning and end of the collection. In the intervening ten stories, Father Brown is alone, and investigating mysteries involving objects as varied as mirrors, literal goldfish (made out of gold), and a suit of armor. As always, his investigations also provide him an opportunity to expound on the nature of evil, the differences between a charlatan's representation of the supernatural and the real thing, and the opportunities for thieves and murderers to repent of their deeds.