The late second century AD. Once more the Roman Empire has been torn apart by a war of imperial succession. Following the Year of the Five Emperors, three are left in the field. A final bloody confrontation between two of them is inevitable as the ruthless Septimius Severus advances through Cappadocia and Cilicia on the heels of the retreating legions of the Emperor in the East, Percennius Niger.

Co-opted into Severus's legions are two veterans who had, after long service, longed for peace. Gauis Rutilius Scaurus, restored to legion commander and his client, the Tribune Marcus Laticlavius Aquila. Unknown to all but a few, Marcus is an Emperor killer. Perhaps this fate beckons him again.

As Niger retreats towards the impregnable fortress of Antioch, thus threatening to extend the conflict for years, it falls to these two men to plan a series of daring raids to delay the enemy.

But it is not long before they are cornered on a climactic field of blood where one or other of the Imperial pretenders must be annihilated.