Edwardian Britain: 1910.
Kora Blackmore, thrown into Bedlam mental hospital by her father – Britain's leading industrialist Sir Tantalus Blackmore – is one day visited by a mysterious gentleman, who gains her trust then makes off with her to his family home in Sheffield. But Kora is afflicted with a bizarre condition, that the hospital believes is a second soul – the girl Roka – somehow living inside her.
Roka however is much more feisty than Kora, and far less obliging. Soon she is caught up in street politics, disorder and protest – and all without Kora's knowledge.
With the agents of Sir Tantalus closing in, Kora and Roka must survive in their new circumstances and with their friends uncover the sequence of events leading to the incarceration in Bedlam; for although Kora is an illegitimate nobody, it seems her upbringing was devised to meet an enigmatic and ghastly end...