This is the fifth part in Francisco Goldman’s series on the recent upheaval in Mexico. He has also written “The Disappearance of the Forty-Three,” “Could Mexico’s Missing Students Spark a Revolution?,” “The Protests for the Missing Forty-Three,” and “An Infrarrealista Revolution.”

In December, revolution seemed possible in Mexico. The source was a nationwide protest movement that some called the Mexican Autumn—ignited by the late-September kidnapping, and then alleged murder, of forty-three students from the Ayotzinapa Normal School, in the small city of Iguala, in the Mexican state of Guerrero. The forty-three were among a larger group of students who were trying to leave Iguala in five commandeered commercial buses that came under a series of armed attacks from local municipal police and other gunmen. Six people were killed in the first hours of the attacks, and forty-three others then seemed to disappear.

Ten days passed before the Procuraduría General de la República (P.G.R.), Mexico’s equivalent to the U.S. Attorney General’s office, began an investigation into the students’ whereabouts. In the months since, a haphazard investigation turned up clandestine grave after grave filled with dismembered bodies. None of them, however, held the students. The world, horrified, discovered the truth about Mexico: that official complicity with organized crime, corruption, and impunity has left ordinary citizens in many parts of the country without protection against predatory violence and lawlessness. The government of President Enrique Peña Nieto and his P.R.I. Party, which had been celebrated abroad for its agenda of neoliberal economic reforms but is much less popular in at home, saw its image of competence—the “saviors of Mexico”—destroyed.

The protests, which emphatically blamed the government for the crime (“It Was the State!”), quieted down over the holidays, especially in Mexico City, when the capital’s secondary schools, colleges, and universities emptied for Christmas vacation. The students had put tens of thousands of young people into the streets. But the parents of the missing group from Ayotzinapa, along with the surviving students, are the movement’s true leaders. The parents told the nation that for them, with their sons missing and their fates still unknown, there would be no Christmas or New Years. On Christmas Eve, in an unseasonably chilly rain, the parents and other relatives marched to the gates of the Presidential residence, Los Pinos, where they were turned away by waiting riot police; on the day after Christmas, there was a march, modest in size, that began at El Ángel, the famous monument on Paseo de la Reforma, and ended not far away, at the Monument to the Revolution, where parents addressed the crowd. You didn’t need to understand Spanish to be brought to tears by the emotion in their voices and words. The parents went out into the streets again on New Years Eve.

Some commentators fretted about an inevitable cooling of passions. On January 23rd, when Amnesty International accused the P.G.R. of having conducted a “deficient” investigation into the disappearances, one of Amnesty’s spokesmen said, “This is what the Mexican government is betting on: they’re betting on forgetting, betting that this will fade.” But then a new semester began. Monday, January 26th, marked four months since the students disappeared in Iguala. Tens of thousands of protesters took to the streets for the year’s first “mega march,” which paralyzed Mexico City. That same day, there were more than forty marches and protest actions throughout the country. The message was clear: Mexicans may like to enjoy their holidays, but they hadn’t forgotten.

The government, meanwhile, wasn’t setting anyone’s mind at ease. In mid-January, the P.G.R., headed by Attorney General Jesús Murillo Karam, formally accused the former mayor of Iguala, José Luis Abarca, of having ordered the municipal police to kidnap the students and turn them over to a group of local drug traffickers known as Guerreros Unidos; his wife, María de los Angeles Pineda, was accused of involvement in “organized crime” for her alleged close association with the group. Abarca, whose party, the P.R.D., has been aligning itself with the ruling P.R.I., had gone into hiding with his wife in October, when the first accusations surfaced; they were captured in November. Two hundred and twenty-one arrest orders have been issued in the case, and ninety-seven people, most of them municipal police officers from Iguala and the neighboring town of Cocula, are now in detention. “All lines of investigation that have arisen during the inquiry have been exhausted,” the head of P.G.R.’s criminal-investigations branch, Tomás Zerón de Lucio, declared at a news conference in mid-January.

According to de Lucio’s investigation, the forty-three students were driven in two trucks to the Cocula municipal dump. During the drive, the investigators estimated that about fifteen students died of suffocation or from gunshot wounds­. At the dump, they were turned over to a handful of Guerreros Unidos sicarios. Three of the sicarios were captured and had confessed that, on orders from their capos, they had murdered the students who were still alive, and then incinerated all of the bodies in a bonfire at the dump, which burned through the night. When the fire was finally extinguished, according to the P.G.R., the sicarios were ordered to clean up the site and throw whatever remains they could recover into a nearby river. Some of these remains were eventually discovered, reportedly, inside plastic bags. Everything was so thoroughly burned, however, that Argentine forensics experts, working with the P.G.R., were unable to recover any DNA. Seventeen samples of the remains found inside the plastic bags were sent to a specialized lab at the University of Innsbruck, in Austria. There, scientists declared that they had identified, from one molar and two centimetres of bone fragment, the DNA of one student, twenty-one-year-old Alexander Mora Venancio. According to Murillo Karam, the identification of Mora, the declarations of some of the detained suspects, and (according to press reports) other information that he did not specify was enough evidence to be able to say that, in the Cocula dump, “at least one was killed.” That, the Attorney General said, “makes me think that they all were.”

The story of the P.G.R.’s “exhaustive investigation” and the announcement, finally, of formal criminal charges against the former mayor and his wife did little to quiet people. One reason is that the charges were long expected. Another was that, ever since people had begun discussing the potential scenario at the dump, earlier in the fall, doubts had grown regarding the P.G.R.’s conclusions. On the day the charges were reported in the newspaper La Jornada, for example, there was another story with the headline “Expert Affirms That the Possibility that the Students Were Cremated in Cocula is ‘Zero.’ ” That story reported on a public presentation given by an National Autonomous University of Mexico professor, Jorge Antonio Montemayor Aldrete, who led a team of scientists from various academic institutions in a study of the government’s Cocula dump-burning scenario. As reported in La Jornada, the study concluded that “incinerating the 43 bodies would require 33 tons of wood … or 995 tires, and these would not have been piled one atop the other but would have had to be spread out over the terrain, requiring 540 square meters,” a space the report indicates is ten times larger than the Cocula dump. Montemayor also noted that, if wood were used, two large trailer trucks would have been needed to transport the load up a slippery and narrow muddy road to the dump. The smoke from the fire would have been visible for miles around. If tires were used, then steel wires, a necessary component in standard automobile tires, would have turned up among the ashes. According to the P.G.R.’s hypothesis, Montemayor said, the September 27th bonfire had reached an unlikely temperature of sixteen hundred degrees centigrade, yet photographs taken in the days after the alleged blaze show abundant grassy growth along the area’s peripheries, an impossibility, according to the scientist, after such an intense fire. Montemayor added that the bodies of the students who were already dead when they reached Cocula would logically have been dragged down the steep slopes of the dump ditch, “so that bits of DNA should have been recoverable from the terrain, such as blood, hair, and even skin that could have struck rocks and been scraped.”