In 140 AD, the Roman Empire extends all the way to Britain - though its grasp is incomplete, as the rebellious tribes of Caledonia (today's Scotland) hold sway in the far North. Marcus Aquila arrives in Britain, determined to restore the tarnished reputation of his father, Flavius Aquila. It was 20 years earlier that Rome's 5,000-strong Ninth Legion, under the command of Flavius and carrying their golden emblem, the Eagle of the Ninth, marched north into Caledonia. They never returned; Legion and Eagle simply vanished into the mists.