The narrative begins in Morelia, Mexico, where Professor Thomas Palgrave meets the devout Franciscan monk Fray Antonio. Palgrave has spent decades preparing to uncover the remnants of the pre-Columbian Aztec world. Through a series of extraordinary chances, Fray Antonio discovers an ancient letter from a sixteenth-century missionary detailing a hidden valley where the Aztec kingdom of Culhuacan and a vast treasure remain untouched. Palgrave concurrently acquires a secret maguey codex and a gold token from a dying mountain cacique.
Joined by two practical-minded Americans, Rayburn and Young, the small party sets out into the rugged mountains. They face intense perils, hostile Indian tribes, and the loss of companions, yet press forward following ancient rock carvings. Descending into a desolate valley, they discover a city submerged beneath the waters of a lake, a grim reminder of an ancient, calculated vengeance.
Continuing their journey, they scale seemingly impassable cliffs and finally reach the hidden paradise of the Valley of Aztlan. There, the modern descendants of the Aztecs welcome them with a mix of awe and religious reverence. The novel explores the deep collision between ancient ritual, Spanish conquest, and the scientific curiosity of the nineteenth century.
