The year is 270 AD.
"Cassius Corbulo is a young intelligence agent fresh from officer training. He has been assigned the menial task of rounding up wounded legionaries but then urgent new orders arrive. He is the only ranking Roman officer left in the line of the Palmyran advance. He must take command of the fort of Alauran, the last stronghold still in Roman hands, and hold it against the enemy until reinforcements arrive."