Evaristo and Luis Antonio - indigenous brothers from the SierraTarahumara in northwest Mexico - have just graduated from boarding elementary school. Evaristo desires to continue his education, leading a bicultural life, where the Tarahumara, or Raramuri as they call themselves, have the opportunity to keep learning to speak, read and write in Spanish, the Mexican official language. Meanwhile Luis Antonio "Tony" is very happy to be done with school. Even though he is a smart kid and has won a grant to move on to high school, he prefers to live life in the ranch, where the kids grow up at a very young age. One morning the brothers are sent to deliver some medicine to a far away community. Tony asks their grandfather for permission to take his horse but the answer is no. Nevertheless, he decides to take it, even if Evaristo is not convinced. They take a wrong path that leads them to a narrow and deep canyon. The horse cannot go on so the boys tie it around a tree. When they come back for it the horse is no longer there. Both, angry and worried, walk in the forest looking for it; Tony thinks the horse was stolen while Evaristo is worried about the assignment. Arguing about this, they suddenly lose each other. Now each on their own continue the journey separately; Tony looks for the horse and ends up at an amusing party, while Evaristo is lonely in the canyons looking for the place to deliver the medicine. The trip becomes longer than expected. They can't go back without the horse.