In 16th century Venice, courtesans (a prostitute to the wealthy) have an abundance of unique privileges that aren't available to usual prostitutes. They dress in red, they are very well read, compose poetry and music, and discuss readily, the affairs of state with the men who govern the republic.
Veronica Franco (Catherine McCormack) has just come of age and is very much in love with Marco Venier (Rufus Sewell). Unfortunately, however, she is unable to marry the one whom she wishes as she is penniless. Well born...but penniless nonetheless.
She has now got to make a life altering choice: succumb to a life in a convent (cloister) or become a courtesan. Needless to say she steals her heart and becomes one of the best courtesan's of her time. But what with her beauty and intelligence this was a foregone conclusion.
Whilst at work, she manages to help convince France to help Venice with their current battle with the Turks. This alone makes her a national heroine. However when the bubonic plague descends on the community, the Church charges her with practicing witchcraft.
During her inquisition she is forced to match wits with one of her oldest rivals, speak for all womankind, and call courage from Venier.