This is a difficult question because The Devil's Highway is told in a kind of flashback. For example, chapter one says five men come out of the desert and are found by a Border Patrol agent; then it backtracks to how they arrived and we meet those five men again in chapter 14. It is also difficult because this is a story of a series of tragedies and missteps, some deliberate and some accidental. If the climax is defined as the moment when everything changes, the author himself says it is when some immigration or other vehicle shines its lights on the nearly exhausted group near Bluebird Pass and they scatter (chapter 8). For me the climax is two chapters later, when their Coyote guide Mendez starts to lose his own reasoning power, collects (perhaps by force) the men's money, and then walks away, promising to return for his group. Of course he had no intention of doing so, and this act clearly marks the beginning of the men's death march.