But when a family trip goes awry, the two Mexican-American cousins from opposite sides of the border accidentally unleash an evil spirit from centuries past. The incident unlocks latent magical powers within the girls, who now have to figure out what's going on. Easier said than done. The only things Ada and Miry know are that the spirit is tied to the pyramids of Teotihuacán, an ancient and abandoned civilization, and that there is only one organization that can help them. The Archivists of Teotihuacán. With only a scant trail of clues to guide them, Ada and Miry must journey across Mexico City, uncover the origin of their powers, and try to reseal the spirit they've awoken. But the hardest challenge of all? Getting along with family.