The book is GLASS HOUSES, by Louise Penny 
This is the 13th of now 14 novels of Montreal police guy Armand Gamanche and the village of Three Pines. But the first time I have read Penny. She writes well, and there are enough twists and turns to keep it interesting. It’s not perfect, but if you like police/who dunnit novels, I recommend.
That’s not the main point of reviewing it here, however. There is in the novel a fascinating character, the cobrador. A little known part of Spanish culture, the cobrador is masked and robed in black and follows around, without saying anything, someone who is a debtor, in order to shame them into paying. When the justice system fails, the cobrador often succeeds. The cobrador is hired by the person to whom the debt is owed, or someone who just wants to see justice done. The cobrador acts as a conscience for people who don’t have one. In Glass Houses, the cobrador acts as a conscience for a different kind of debt.
I think it’s a fascinating theological concept. Is it the opposite of Jesus when he teaches us to pray for forgiveness of debt, rather than payment of debt, or is it the same thing in a different costume? Discuss among yourselves.
BTW, Marcus Borg says that debt is probably the most accurate word to use in praying the Lord’s Prayer, rather than trespasses or sins, because of the importance of debt in the time of Jesus, the domination class using debt to keep poor people under control. The way mine owners did with coal miners via the company store [St. Peter, don’t you call me, ‘cause I can’t go, I owe my soul to the company store] and the way land owners do with tenant farmers.
Glass Houses is a Christmas gift to Helen from daughter Katie Kennedy and her family. Most of our books come to us as gifts from our daughters. That’s a good thing, because they both know good books from the others.