Father Brown au where Kembleford is a demimonde; the majority of families and people are either completely or partially magical, with Inspector Sullivan and Father Brown being just about the only humans.
Mrs McCarthy is a witch, even if she doesn't get much on her broom these days ('Not with the state of my knees!'). Lady Felicia and Bunty are descended from sirens, and Sid is descended from the fey.
Flambeau's family worshipped old gods, and Mallory and Goodfellow are both descended from gnomes, although in Goodfellow's case, Red Caps ('I like a rare steak every now and then, but the aggression was bred out of the family decades ago').
oh oh, I made a Father Brown series 10 bingo card!! some of these things we know we're getting, some were pretty sure we aren't but are being hopeful anyway, some we have no idea, but that's the fun!!