Emperor Justinian II was overthrown, his nose was cut off, and he was sent into exile in distant Crimea. Escaping from captivity, Justinian swears to take revenge not only on the usurper of the throne, but on all the former subjects as well. He leads into the empire a hired army, headed by the northern warband of Mstvelda—invincible Vikings—and the cavalry of the Bulgarian хан Tervel, son of the famous Asparukh. The Slavic warrior Lubenya too makes a vow to the gods—to take revenge on those who stole his beloved and to find her alive or dead. He joins the Vikings and fights in Byzantium, searching for the girl. Will the warrior manage to find her? Will the emperor’s troops storm the impregnable Constantinople?