Viola has an impossible talent. Searching for meaning in her grief, she uses her photography to feel closer to her late father, taking solace from the skills he taught her - and to keep her distance from her husband. But her pictures seem to capture things invisible to the eye . . .

Henriette is a celebrated spirit medium, carrying nothing but her secrets with her as she travels the country. When she meets Viola, a powerful connection is sparked between them - but Victorian society is no place for reckless women.

Meanwhile, on the other side of the world, invisible threads join Viola and Henriette to another woman who lives in secrecy, hiding her dangerous act of rebellion in p