Emperor Justinian has sent Belisarius to Britannia to do what no one has ever done—conquer the Picts. The army that gathers at Hadrian's Wall includes an airship legion. One of those airships and its sagittarii, who fight as archers in the sky and as soldiers on the ground, are commanded by Cillian. His concerns about the campaign, his airship, and his destiny are about to be overtaken by a hidden past revealed. To reach the Picts, Belisarius's army must cross over the ruins of another wall, the Antonine Wall. But the Picts are not alone, and they are not the only threat, and the war will not be what anyone expected.