A temple precinct on the edge of the Aztec empire still keeps the old predawn lake bath, the smoke offerings and the conch sounded at the hours. For three acolytes, their days follow a rigid course of study and duty — but hidden codices in the library hint at practices the elders will not discuss. Seeds of ololiuqui are ground for ceremonies the priesthood has begun to perform without witnesses.

Teo is brushed by harmonies he cannot name. Yolma reads what the codices were never meant to show. Lalli hears what others have decided not to say. They are sworn to the temple and to one another, but these oaths quickly come into conflict.

As they try to untangle their own ordeals at the temple, word reaches them from the coast: pale strangers have landed, with weapons that strike with thunder. The trail leads to the Templo Mayor and to a court where Cortés, Marina, and Alvarado now move freely. The elders say the prophecies are speaking; the imperial messengers say the empire will absorb it all. The acolytes begin to piece together divine implications: the Fifth Sun is straining, and the gods themselves are at war over what comes next.