FatherBrowntriestotransportahistoricallyimportantcrosstoRomeengaginginbattlesofwitsandfaithwithathiefandpursuingpoliceman.Thethief,namedFlambeau(Finch),isamasterofdisguiseandiselusive,asFatherBrownpursueshimandtriestoconvincehimtoabandonhiscriminalcareer. Duringthemakingofthefilm,AlecGuinnesswasmistakenbyasmallboyforanactualpriest.ThisepisodeappearstohaveplayedapartinGuinness'slaterconversiontoRomanCatholicism.
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