One primary theme of Valeria Luiselli’s novel is the impermanence of geographic borders. As the family travels toward and through the US Southwest, they encounter numerous physical boundaries between locations that have lost their past importance. A tightly intertwined theme is the relationship between those physical boundaries and conceptual ones. The latter include the theme of race and ethnicity as central elements of US culture. Concern with language is paramount in the theme of communication both through oral and written media, as connected with those conceptual borders. The novel is deeply involved with the fragility of children, many of whom are vulnerable undocumented immigrants who do not actually appear in the novel because they have gone missing. More generally, change over time is a continuous thread running through the novel.
The relationship of present and past is played out through the two central characters. The unnamed narrator is a journalist whose work concerns the undocumented children, while her husband, sometimes called Papa, is an ethno-audiologist specializing in Native American and ancient sound and language. Their professions thus offer a contrast, as her concern is with contemporary events and his is with past occurrences. However, the heritage of indigenous Americans is very much part of the present in the Southwestern territories they traverse in their car. Much of the novel consists of the family’s road trip, offering diverse perspectives on the racial and ethnic boundaries as they constantly shift across the US landscape in the Southern border zone.
The couple’s children—one each from previous relationships—are traveling with them. Both children are US citizens, so their youthful perspectives on the plight of the undocumented children, many of whom are unaccounted for, are especially poignant. In addition, the conceptual boundaries relate to communication problems within the family. The joining of the families is relatively recent, so the challenges of working through those challenges, as the mother’s concern for the missing children sparks worries about their own children, becomes a recurrent motif.