At the end of 1899, in the Mexican state of Sonora, National Rural Policeman Miguel Ángel Ibarra, recovering from a small stroke that has changed his view of the world, begins to think that the rights described in the Mexican Constitution of 1857 should also apply to the Yaqui Indians, whom first the the Spanish, then the Mexican governments, had been trying to wipe out for hundreds of years. This new conviction marks him as an enemy of State and Federal forces and throws him into a deadly situation, as he tries to solve a robbery committed against an American-run mine in the Bacatete Mountains east of Guaymas. There he stumbles onto a dark secret when he comes into contact with Yaqui miners.