Olivia's life is hanging by a thread. Hunted as a spy by the British Empire, and now by her own countrymen, she needs to do the impossible to survive - bring the Empire to its knees. The company forging a golden age of steam for the Empire is the Fanshaw & Fotherington Electro-Mechanical works. Destroy it and the British Empire will follow. But before Olivia can put her deadly plan into motion she must first locate the almost mythical creative heart of the Double-F company - the Squirrel Works - run by the reclusive Tiberius Fanshaw. The seed of its destruction is a secret hidden for many years concerning Nathaniel, the son of a widowed London steam-cabbie. Now he is caught in Olivia's deadly web his life is in dire peril. But what hope has Nathaniel when, in order to save her own life, Olivia must destroy two empires?