Major Themes Walls The building of literal walls is not a hidden theme in the novel much of the controversy from the start concerns the building of first a gate and then a wall for Arroyo Blanco and the entire novel is based on the consequences of immigrants jumping the wall of the Mexico U S border The literal wall appears in several other ways as well The coyotes must get over the Mossbachers fence in order to grab their dogs and they are able to do so with skill and cunning similar to the wa