Isabel Aird is aghast when her husband is appointed doctor to an extraordinary waterworks being built miles from the city. But Isabel, denied the motherhood role that is expected of her by a succession of miscarriages, finds unexpected consolations in a place where she can feel the presence of her unborn children and begin to work out what her life in Victorian society is for. The hills echo with the gunpowder blasts of hundreds of navvies tunnelling day and night to bring clean water to diseased Glasgow thirty miles away – digging so deep that there are those who worry they are disturbing the land of faery itself. Here, just inside the Highland line, the membrane between the modern world and the ancient unseen places is very thin. With new life quickening within her again, Isabel can only wait. But a darker presence has also emerged from the gunpowder smoke. And he is waiting too.