This is an alternate history novel, set at the time of the collapse of the Roman Empire. The empire has split into three hostile fragments. The Eastern Empire, under Emperor Justinian, has sent his army, commanded by General Belisarius, to invade Italy.
The Western Empire knows that if Belisarius succeeds in Italy, they will be next.
Gaul, poorer and weaker than the East, depends upon its aviators to patrol the frontier and bring news of any threat. They operate the messenger service that holds the Western Empire together.
Marcus has joined the aviators in Britain, hoping to avoid politics by following the life of a pilot. But his plan has failed, and he has been pushed to the centre of power. Then the Western Emperor asks Britain to send a contingent of soldiers to defend Italy.
Antonia's father, accused of treason, has fled from Constantinople with his family. They have found refuge in Rome and are trying to avoid the attention of the Eastern empress, Theodora.
But now Justinian's army is marching on Rome.
Marcus has found success as a junior officer. But fate intervenes once more, and he meets Antonia's family.