London 1937. When Adelaide Anson-Gravetty discovers she is not who she thought she was, her search for her true family leads her to the convent of Our Lady of Mercy in St Croix in northern France. The defeat of France brings German occupation to the village, the nuns are caught up in a war that threatens both their beliefs and their lives. Involved with the resistance and British agents, Adelaide and the sisters truly walk in the shadow of death as they try to protect the innocent from the evil menace of the Nazi war machine.