The two main characters are Quintus Licinius Cato and Lucius Cornelius Marco. Marco is a centurion who has been a member of the Roman Army for years and is good at his job, killing people. He is illiterate, follows orders and is dependable, Cato on the other hand is a freed slave, who likes literature, is physically weak, and a fish out of water. Due to political reasons Cato is made Optio and is therefore Marco's second in command. No one treats him with any respect and they resent his quick rise to officer ranks when he hasn't proven himself capable of anything.
The series follows their adventures through Britain and into Judea as Marco and Cato fight with the Legions and get involved in political struggles within the Empire.
There is no danger of accusing Scarrow of originality in these novels, but they fly along at a cracking pace and don't let the reader down for a second. Scarrow's research and love for this period shine through, and help to make the series so easy to read.