A man from our time, Aleksei Terekhin, an officer of the courier service, after a passenger airplane crash becomes the owner of an unusual artifact that transports him to Ancient Byzantium. Thanks to his officer training, he rises from a mercenary hoplite to become a tribune, commander of the chiliarchy—climbing through all the hierarchy levels of the army. Owing to his steadiness, personal courage, and intelligence, Aleksei manages to become a blood brother of the commander of the army of Ostris and carry his friendship through the centuries.