Sally is sixteen and uncommonly pretty. Her knowledge of English literature, French, history, art and music is non-existent, but she has a thorough grounding in military tactics, can run a business, ride like a Cossack and shoot straight with a pistol.

When her dear father is drowned in suspicious circumstances in the South China Sea, Sally is left to fend for herself, an orphan and alone in the smoky fog of Victorian London. Though she doesn't know it, Sally is already in terrible danger. Soon the mystery and the danger will deepen - and at the rotten heart of it all lies the deadly secret of the ruby in the smoke...