Father Dowling has a twin brother who gets him into trouble in this episode and previous one "The Face in the Mirror Mystery".
Father Dowling is having a special mass for kids that are getting their First Communion in church an a woman walks him and accuses him of being her lover and a hypocrite.
He is embarrassed she stopped the mass and yelled for everyone to hear. The accusation may ruin his reputation so him and Sister Steve try to clear his name.
The woman is the owner of a cosmetic company and she works with relatives who want to make changes.
She later turns up dead. Father Dowling figures his twin brother Blane Dowling is the one that had the affair with the woman. Blane is known to be a womanizer and the woman like him.
Father Brown and Sister Steve watch one of the employees of this company related to the woman that was murdered. They figure it has got to be someone she worked with or knew.
It has a surprise and funny ending. Watch it while you can on Youtube. http://www.youtube.com/watch?v=rf4tPPnyYAc