On September 26, 2014, 43 male students from the Ayotzinapa Rural Teachers' College went missing in Iguala, Guerrero, Mexico. On route to a protest, local police intercepted the students and a confrontation ensued. By the morning, they had disappeared without a trace.

Hernández reconstructs almost minute-by-minute the events of those nights in late September 2014, giving us what is surely the most complete picture available: her sources are unparalleled, since she has secured access to internal government documents that have not been made public, and to video surveillance footage the government has tried to hide and destroy. Hernández demolishes the Mexican state's official version, which the Peña Nieto government cynically dubbed the "historic truth". As her research shows, state officials at all levels, from police and prosecutors to the upper echelons of the PRI administration, conspired to put together a fake case, concealing or manipulating evidence, and arresting and torturing dozens of "suspects" who then obliged with full "confessions" that matched the official lie. By following the role of the various Mexican state agencies through the events in such remarkable detail, Massacre in Mexico shows with exacting precision who is responsible for which component of this monumental crime.