The unexpected friendship between Tabitha Prewett, the only daughter of a tailor, and Mariette de St Aubyn, daughter of aristocratic French imigris, deepens as the years pass, rising above their differences in social class and religion. But when Mariette marries Conor Townclear, Tabitha's emotions are stirred. As angry rioters flood through London during violent anti-Catholic riots, leaving mayhem in their wake, the three of them are drawn together in life-threatening circumstances.