Father Brown’s work as a priest causes him to take a spiritual approach to his detective work, using his understanding of human nature and morality to solve crimes. He explains to Hercule Flambeau in “The Blue Cross” that he “does next to nothing but hear men’s real sins” and is therefore highly aware of “human evil” (15). Throughout the collection of stories, the complexity of good and evil in humanity is prevalent in the individual cases. Father Brown’s work proves that even good people can do terrible things under the right circumstances, while even seemingly bad people are capable of reform.

Flambeau is an intelligent thief but underestimates Father Brown initially. This mistake leads to his arrest. Aristide Valentin is a good, honest man who wants to bring justice, but his disdain for religion and the Catholic Church leads him to commit murder and hide the evidence in “The Secret Garden.” Unable to deal with the consequences of what he has done, Valentin dies by suicide after Father Brown discovers the truth. Similarly to Valentin, Reverend Wilfred Bohun in “The Hammer of God” is a good, honest man whose rigid value system leads him to commit an uncharacteristic and brutal act of violence against his brother.