It is 1877, and war has broken out between Russia and the Ottoman Empire. The Bulgarian front resounds with the thunder of cavalry charges, the roar of artillery, and the clash of steel on steel during the world's last great horse-and-cannon conflict. Amid the treacherous atmosphere of a 19th-century Russian field army, former diplomat and detective extraordinaire Erast Fandorin finds his most confounding case. Its difficulties are only compounded by the presence of Varya Suvorova, a deadly serious (and seriously beautiful) woman with revolutionary ideals who has disguised herself as a boy in order to find her respected comrade, and fiance, Pyotr Yablokov, an army cryptographer. Even after Fandorin saves her life, Varya can hardly bear to thank such a "lackey of the throne" for his efforts.