Born in the Greek city of Thessaloniki, Constantine is a very clever child. Alongside his brother Michael, later known as Methodius, Constantine grows into a fine young man as he grapples with the world's expectations for him.
Prince Rastislav of Moravia requests Christian missionaries from the Byzantine king Michael II. Michael sends him Constantine and Methodius, who are tasked with creating an alphabet for the Slavic people of Moravia.
Despite the popularity of their teachings, Constantine and Methodius face opposition from the Frankish priests of Moravia. After being accused of heresy, the brothers must journey to Rome to prove their legitimacy with the Pope.
After Methodius returns to Moravia alone, he finds himself in the midst of plenty of political unrest. The Frankish priests do not wish to give up control of Moravia to Slavic liturgy. Chaos ensues.