In 304 c.e. Aelius Spartianus, officer and historian at the court of Diocletian in Dalmatia, is writing the biographies of past Roman rulers, including Hadrian, who has been dead for nearly 175 years. Aelius's particular charge is to investigate the unsolved mystery of the drowning death in the Nile of Hadrian's favorite, young Antinous. Soon his duty turns twofold: the hunt for Antinous's grave, supposed to conceal proof of a conspiracy against Rome,...