1/ At risk of plagiarizing a @niallgooch (I haven't seen it but it seems likely he's said it before), "clerical detective stories" are a popular/significant part of the mystery trade for a few reasons, but here's the main one: priests deal with sin. Sin is real, and scary, and...

2/ becomes undeniable in the context of crime. Clerical detectives often bring hope of both divine justice and of forgiveness and reconciliation. Cadfael stories always include a romantic subplot where he helps the lovers (even, sometimes, when one of them is a justified killer!)

3/ Father Brown doesn't really bother with temporal justice, but he does try to save the souls and indeed the lives and freedom of the criminals.

You see this spill into adaptations of non-clerical detectives, too. Consider two recent Poirots.

4/ David Suchet increasingly inserted a deep religiosity into his interpretation - not just a reflection of his own faith, but also of the great spiritual matters at stake in murder.

On the other hand, the Malkovich Poirot is a failed priest, someone who *cannot* believe in...

5/ ...positive meaning or objective justice anymore. But even in that interpretation, it is plainly the tugging of his old moral compass that makes him so determined to aid the innocent and punish the wicked.

Of course, that loss of faith makes for a far darker take.

6/ Christie's nearest thing to a clerical "detective", properly speaking, so far as I can think, isn't in fact the "cleric" in the story. I'm thinking of Satterthwaite, in the Quin stories. Old man who befriends a bizarre force of nature masquerading as a human being.

7/ The Harley Quin stories certainly emphasize divine justice and the triumph of lovers (Quin is "Friend of Lovers) - but as it's all viewed through the sidekick-narrator, it's all the more baffling and disturbing. Things just...happen. Reflective of a loss of the orderliness of

8/ faith/institutional religion.

By the way, this idea of clerical detectives as representative of divine justice and mercy stretches to video games. The Shivah is an adventure game about a Rabbi investigating the death of an ex-friend, including an interrogation minigame...

9/ where the way to gain info (or win fights) is to answer everything with a question, Rabbi-style.

The game is humane, desirous of understanding, sensitive to the nature of loss. Justice and reconciliation are real themes.