Twelve-year-old Petra Peña lives on Earth in the year 2061. She is spending the evening with her grandmother, Lita, who is a traditional storyteller, or cuentista. She tells Petra the myth of Halley’s Comet and explains that it is really a blind fire snake in the sky trying to reunite with its mother, Earth. Unfortunately, the comet will strike the Earth on its next pass, so many people are being evacuated to colonize distant planets. Lita is staying behind, and Petra is heartbroken. Lita comforts her by telling her that she’ll always be with Petra in spirit, especially because Petra will tell the cuentos to new generations.

The next day, on the way to the ship’s launch site in Colorado, Petra is conflicted about the fact that her family will get to live while everyone else on Earth will die. She also recalls a television show her parents watched about a group of people known as the Collective that wants to erase all the differences in humanity to create permanent peace. Petra’s father is wary of the way the Collective intends to create harmony in the new world by eradicating diversity.