Phaedrus is persuaded, accepts the role of Midir, the original prince whose eyes were put out by the queen, preventing him from ruling, and receives a signifying tattoo on his forehead, the eponymous Mark of the Horse Lord.

The stage is then set for a struggle between King and Queen, between Dal Riada and Caledones, between the Sun God and the Great Mother; a theme used in many Sutcliff novels.

[2] Phaedrus spends time in a town on the Northern Wall, learning his role from the original prince Midir and the culture of the Celts.

Several historical subjects are discussed, including Lollius Urbicus and the laying-waste of Valentia after subjugation, the Pax Romana and its effects, Calgacus's battles against General Agricola, and the viewpoints of Tacitus on all of this.

He is offered freedom at a great cost to the Dal Riada, referencing back to the discussions of Pax Romana and Roman treatment of the native tribes.