Cantú has a strong relationship with his mother, who appears throughout the book via in-person visits and phone calls.

She raised Cantú in the American Southwest. The daughter of a white mother and a Mexican immigrant, she had a successful yet complicated career as a park ranger for the US National Park Service. She passes her love and respect for Mexico, as well as her love of nature and the desert, on to Cantú, who feels drawn to the desert landscape as an adult. Her experience as a park ranger also makes her wary of government institutions, particularly ones that control land and people, and she warns Cantú of the dangers of supporting these institutions and the ways they can become a part of you. She fears for his safety and well-being while he serves in the Border Patrol, and she allows him the space and vulnerability to feel sadness and grief for José’s deportation.

Morales is a Border Patrol trainee alongside Cantú in Part 1. He grew up in the town of Douglas on the US-Mexico border. They serve together in the field, intercepting migrants trying to illegally cross the border until Morales is hurt in a serious motorcycle accident. This incident, and visiting Morales in the hospital, unsettles Cantú.

Later in the book Cantú calls for a favor from Morales while trying to help Lupe locate José while he is in Border Patrol custody.

Cole is Cantú’s first Border Patrol supervisor while working out in the field; he teaches Cantú how to track migrants in the desert. He goes by the nickname “Black Death.” Cole often cuts corners and tries to avoid situations that require doing more paperwork. Cantú stays in contact with Cole after he is transferred to an intelligence position.

Hayward is Cantú’s career-minded supervisor in the Border Patrol intelligence office. Cantú transfers to El Paso alongside Hayward and accompanies him on a mission trip to New Mexico. Hayward’s ultimate goal is promotion to a position in DC. Over time, Hayward opens up to Cantú about his own experiences in the field as a young man in Virginia, and the one time he had to kill a man. He thinks highly of Cantú and looks out for him.

Beto is one of Cantú’s colleagues and team members in El Paso serving under Hayward. He offers Cantú a place to stay in his backyard casita. He has family in Juárez, and he and Cantú know the dissonance that comes with having Mexican American heritage while serving in the Border Patrol. He becomes a close friend of Cantú’s during his time in the Border Patrol.

José is an undocumented immigrant from Oaxaca who works as a maintenance man. He meets Cantú when Cantú begins working as a barista. They grow close over the course of two years, sharing food and news about Mexican politics and drug cartel violence. When José disappears from work for three weeks, Cantú learns that he is undocumented and has been arrested at the border for trying to cross back into the United States after visiting his dying mother in Oaxaca. Cantú assists José’s wife Lupe and their three sons as they try to get him released. José is ultimately deported several times. In Part 3 the text shifts to allow José to speak in his own voice, making clear that he’ll never stop trying to cross to be reunited with his family, even if it means he is incarcerated or killed.

Lupe is José’s wife. She is also undocumented, and the mother of their three sons. Cantú meets her after José is arrested and translates for her because she is not fluent in English. Because of her undocumented status, she cannot visit José while he is held in the detention center or she will risk arrest herself. She will stop at nothing to try and reunite with her husband, even if it means losing money to coyotes or risking injury.

Diane is the owner of the mercado where Cantú and José first meet. She provides financial support for legal services to José, Lupe, and their family as they navigate José’s deportation proceedings.