The local art gallery has the priceless painting 'The Judgement of Man' on loan from the Vatican and curator Binkie Cadwallader is flattered to be interviewed by the glamorous reporter Rebecca Himmelbaum. Father Brown is convinced that Flambeau is out to steal it and is proved right when Lady Felicia's gallant new American friend Chip Corner turns out to be the thief in disguise. But there is another miscreant out to steal the painting and Rebecca has her own agenda, to punish Binkie for a wartime betrayal.As a result Father Brown and Flambeau enter into a bizarre alliance and Flambeau proves to be more principled than the priest thought.