Titular Advisor Erast Fandorin took part in military operations during the Russian-Turkish War of 1877-1878. Being a Serbian volunteer, Erast Petrovich meets a charming young lady, Varvara Andreevna Suvorova, who is heading to the location of the Russian troops to see her fiance. With her help, Fandorin manages to unravel a complex and mysterious espionage case…