Persia has crushed the Ionian revolt and is gathering a massive army to invade and punish mainland Greece, but in Sparta the dangers seem closer to home. The Eurypontid king Demaratus is accused of being a usurper, while the Agiad king Cleomenes is going dangerously mad. More and more Spartans turn to Leonidas, Cleomenes's half-brother and son-in-law, to provide leadership. But Leonidas is the younger of twins, and his brother Brotus has no intention of letting Leonidas lay claim to the Agiad throne without a fight.

This novel follows Leonidas and Gorgo as they steer Sparta through the dangerous waters of domestic strife and external threat, working together as a team to make Sparta the best it can be. But the forces that will destroy not only Leonidas but his Sparta are already gathering -- not just in Persepolis and Sardis, but in the hubris of a rising Athens and the bigotry and xenophobia of his fellow Spartans. The murder of two Persian ambassadors by an agitated Spartan Assembly sets in train the inevitable conflict between Sparta and Persia that will take Leonidas to Thermopylae -- and into history.

This is the third book in a trilogy of biographical novels about Leonidas and Gorgo. The first book, A Boy of the Agoge, described Leonidas's childhood in the Spartan public school. The second, A Peerless Peer, focused on his years as an ordinary citizen. This third book describes his rise to power, his reign, and his death.