This is the tale of three women - one witch, one mermaid and one missing - and how Ruby was caught up in between.

When Isa Fly appears in the doorway of Captin Len's Fried Fish Shop, thirteen-year-old Ruby is entranced. Isa comes from the coast where the air is fresh; unlike Ruby's home in Cradle Cross, its factory furnaces pumping and filthy slits of canal water sending up a stink.

Isa is on the hunt for a missing person, and Ruby is eager to help, convinced she will be repaid with an adventure at sea. But some of the townsfolk are instantly suspicious of the outsider with her shock of white hair and glinting mirrored skirts. They have their own lost relatives to mourn, and don't take kindly to Isa's ability to leave their Ruby spellbound.

Undaunted, Ruby introduces Isa to Truda Blick, the bluestocking graduate who has just inherited the town's button factory, where carcasses are rendered down and bones turned into buttons. Blickses is on the verge of collapse, and Truda has her work cut out. Ruby is desperate to help Truda and Isa but her alliance with the women is pushing the town to the brink of riot. All the trouble began, it seems, when Isa Fly arrived in Cradle Cross...

Only Ruby knows enough to save them all. But first she must save herself.