After countess Felicia turns down intimidating attempts from Russian tycoon Nicholai Solovey to buy 'baclk' a priceless Russian diamond necklace she inherited from her mother, hence keeps out of the massive assets sale to offset her husband Monty's bankruptcy in a Rhodesian diamond mine, it is stolen and inspector Malory disregards him as suspect. Father Brown test he man and mobilizes an unusual team to steal it back, with lady Felicia as sexy maid distracting the goon, Bunty as casino opponent, dodgy local hotel employee Daniel Winks as bellboy and croupier, and a dangerous secret weapon. Mast thief Flambeau accepts to help Brown, unpaid, only because Solovey once set him up as scapegoat for another theft. The elaborate plan works despite snags, albeit Flambeau give sit his own twists.
—KGF Vissers