Twins, Keziah and Tilly Lovell, are identical in every way, except that Tilly hasn't grown a single inch since she was five. Coerced into promoting their father’s quack elixir, the girls are eventually sold to a mysterious Italian, known only as ‘Captain’.

Theo, an orphan raised by his wealthy—and resentful—grandfather spends his days in an opulent country home. When his grandfather remarries, Theo is forced to leave his home without a penny to his name and takes on work as an assistant in Dr Summerwell’s Museum of Anatomy. And it is here that the lives of the two sisters and Theo collide, with devastating effect.