The story begins in the convent of Our Lady of Rheims, a nursing order near Norwich in England, which has become a refuge for stranded travelers and residents driven from their homes by rising floodwaters. Sarat Cahn is being transported to Norwich prison to be hanged after being convicted of murdering her brother, when the storm forces the guards to bring her to the convent to shelter. Despite Sarat's hostility towards the sisters of the convent, Sister Mary Bonaventure believes that she is innocent, and sets out to prove it, before the flooding subsides...