Britain, 55 BC: Julius Caesar’s invasion of the wild and mineral-rich land is becalmed, a stalemate exists between the forces of Rome and Britain. But the standard bearer of the Tenth Legion, Lucius Oppius, is about to display a depth of courage that will change the course of the invasion - and history. Encamped upon the south coast Caesar, admiring the courage and skill of his standard bearer, orders Oppius to accompany a native British archer and go behind enemy lines.

25 BC. Titus Cervianus is no ordinary soldier. A former surgeon from the city of Ancyra, he's now a capsarius—a combat medic. Cervianus is a pragmatist, a scientist and truly unpopular with his legion. The Twenty Second Deiotariana have been sent to deal with uprisings and chaos in Egypt. Yet the Twenty Second is no ordinary legion either. Founded as the private royal army of one of Rome's most devoted allies, the king of Galatia, their ways are not the same as the other legions, a factor that sets them apart and causes friction with their fellow soldiers. 

It is 58 BC, and the mighty Tenth Legion, camped in Northern Italy, prepare for the arrival of the most notorious general in Roman history: Julius Caesar. Marcus Falerius Fronto, commander of the Tenth, is a career soldier and long-time companion of Caesar's. Despite his desire for the simplicity of the military life, he cannot help but be drawn into intrigue and politics as Caesar engineers a motive to invade the lands of Gaul.

Winter 1644, the Tower of London. Colonel George Monck has been charged with high treason. A brilliant soldier, admiral and military governor, Monck joined the King's men in besieging Nantwich. But the Parliamentary side's more disciplined army successfully routed them, and Monck was thrown in jail. Brooding and despondent, Monck's troubles look to intensify when he starts an affair with Anne Ratsford, a married woman who is caring for him in The Tower.

Veteran cavalry commander Marcus Flavius Victor sets out with his regiment to make what may be his final tour of the forts along Hadrian's Wall. Through a combination of military prowess, brutality and bribery, Marcus has spent 20 years keeping the savage Picts at bay. Feared by his enemies and hated by his superiors, his strength of will is the only thing that has held the disgruntled, poorly paid garrisons of the Wall in place as the failing Roman Empire's grip on Britannia weakened.