In a church in Battersea, Mary-Margaret O'Reilly sees blood on her hands and believes she has witnessed a miracle. The consequences are both profound and devastating - not just for her but for others, too: Father Diamond, the parish priest, struggling with his own faith. Stella, adrift in her marriage and aching for her ten-year old son, away at boarding school. Alice, counting the days until her soldier son comes home. And Mary-Margaret's mother, imprisoned in a tower block with nothing but her thoughts for company...