The Ruby in the Smoke — Philip Pullman

"Beware the Seven Blessings..."

When she first utters these words, Sally Lockhart doesn't understand their meaning. But when an employee of her late father hears them, he dies of fear. Thus begins Sally's terrifying journey into the seamy underworld of Victorian London, in search of clues that will solve the puzzle of her father's death. Pursued by villains and cutthroats at every turn, the daring 16-year-old heroine uncovers two dark mysteries. One involves the opium trade; the other, a stolen ruby of immense value. Sally soon learns that she is the key to both--and it's worth her very life to find out why.