Mark is a young British sailor who is deployed to Antioch in Syria as part of a delegation to brief the Emperor Diocletian on the liberation of Britain from a usurper. By coincidence, he meets the Tribune Constantine who introduces him to a fellow Roman Army officer, George. Mark can write in Latin so George appoints him as his clerk.
Mark is tasked to keep an account of the operations of the 'special forces' unit that George commands on the front line of the Eastern Roman Empire. He also keeps his own private diary and is required to provide Constantine, who is a member of Diocletian's personal staff, with periodic accounts of operations.
As George achieves some extraordinary results and Diocletian manages to stabilise the Roman Empire following a generation of chaos and uncertainty, a new problem arises. Diocletian's deputy, Caesar Galerius, starts seeing Christianity as a subversive religion. This becomes a challenge for George, his family, and some members of his unit.
This is the tale of Constantine and George, told through the eyes of a young soldier's diary.