The Scarlet Borders mark the boundary between the empire of Jephraïm and the kingdom of Bakara. During an attack led by Bakareans, Yaël, daughter of the Commander of the Empire's armies, witnesses her father's murder at the hands of Nyx the spy. Nyx takes Yaël to Bakara in order to convince her that Bakareans are not the barbarians the Empire claims; rather, it is the Emperors who are. Meanwhile, Nyx's spy brother Helios infiltrates the Empire's First Guard. His mission? To kill the Emperors. But he can't help taking a shine to one of them, or admiring the persona and authority of another other. Yaël, Nyx, and Helios will have to fight many battles to make sure truth wins out.