RISING FROM THE ENDLESS SEA is the Vertical Horizon, a massive rock spire holding four tiers of kingdoms. Four Truth Stones, one for each of the spire’s interdependent tierdoms, help maintain a delicate power balance. But when a stone is stolen, the Spire is plunged into war.

Seventeen-year-old Princess Aratess of Ardenia is destined for the shallow life of the royal court—and an arranged marriage to a selfish prince—but she longs to serve her people in a different way. For years, she’s practiced archery in secret, and when the chance arrives, she matches her talents against Colt, an elite King’s Bowman.

Fiercely loyal to the crown, twenty-year-old Colt questions how his mother’s people, the Reyjik, could betray the Realm. He also questions the judgment—though not the skills—of the fiery young woman who has inserted herself into his mission. Tess keeps her identity a secret, knowing Colt would forbid his princess from risking her life. Colt, meanwhile, strives to keep a secret of his own: his growing feelings for Tess.

As Reyjik overrun Costair’s capital, Colt and Tess escape skyward to warn the King of Ardenia and mount a counterattack. Desperate, they enlist the help of Deacon, Colt’s estranged childhood friend and a lighter-than-aircraft pirate. Will Colt, Tess, Deacon, and a motley crew of pirates prove enough to stave off invasion and turn the tide of war?