Nothing

"...You'd have asked a manufacturer about the conditions of his factory; but nobody seems to consider the conditions under which poetry is manufactured. It's done by doing nothing." - Father Brown in The Mirror of the Magistrate by Chesterton



On a different note, there is no depiction of Father Brown whether on film or in TV that even comes close to the books. Most of them seem to settle for the quirky outward appearance of Father Brown but seem to miss that if anything he is a sort of profiler, though not exactly for he admits that he solves the crimes by committing them himself. The other topos that he is constantly in trouble with his superiors is also something that can not be found in the books, instead he states once that solving crimes or rather sins was suggested as a clerical or spiritual exersise to him.