Pope Francis heads into the capital's crime-ridden suburb of Ecatepec on Sunday to see firsthand the reality of the Mexican "periphery," where drug violence, gangland-style executions and kidnappings are daily facts of life.
The pontiff is expected to bring a message of hope and solidarity to residents with a Mass featuring readings about not being tempted by the devil -- a common exhortation from a pope who frequently invokes the threat of "the evil one."
The Mass is to take place at an outdoor field with an estimated capacity of 400,000, and the pope's choice of Ecatepec for what figures to be his biggest event in Mexico says volumes about his priorities.
The city of some 1.6 million people is a sprawling carpet of cinderblock slums mixed in with some better-off neighborhoods. It's also a strategic point for drug gangs that thrive amid poverty, unemployment and impunity.
It will be a strikingly different backdrop from the pageantry of Friday night's red-carpet welcome at the Mexico City airport, where President Enrique Pena Nieto and first lady Angelica Rivera greeted Francis alongside performances by folkloric dancers and mariachi musicians.
Conchita Tellez, 65, from the northwest Mexico border city of Mexicali, said she spent 38 hours on a bus to get to Ecatepec and was among the first in line for a spot at the Mass. She expressed hope Francis can help ease the troubled soul of the country, where 100,000 people have been killed and 27,000 disappeared in gangland violence since Pena Nieto's predecessor launched an offensive against drug cartels shortly after taking office in late 2006.
"The pope comes to Mexico at a very ugly moment," Tellez said, "and he comes to pray for us and for all those who lost hope and have submerged the country in blood and violence."
Francis' is visiting Ecatepec a day after his grueling schedule appeared to be already taking a toll. He seemed tired and winded at times Saturday, and he appeared to nod off at an evening Mass and also lost his balance and fell into a chair set up for him to pray.
The first two days of the 79-year-old Francis' trip were filled with back-to-back public events and he logged dozens of kilometers (miles) standing in his popemobile in Mexico City while adjusting to a seven-hour time zone difference from Rome. The capital's more than 7,200 feet (2,200 meters) of altitude can also be a challenge for anyone not acclimated, perhaps more so for Francis who lost part of one lung as a young man.
On Saturday, he issued a pair of tough-love messages to Mexico's political and church elite, telling them they have a duty to provide security, justice and courageous pastoral care.
Speaking to the president and other members of government at the National Palace, the pope said public officials must be honest and not be seduced by corruption and privilege that benefits the few to the detriment of the many.
In a subsequent address to his own bishops, he challenged church leaders known for their deference to Mexico's wealthy and powerful to denounce the "insidious threat" of the drug trade and be true pastors instead of career-minded clerics who spew inoffensive denunciations that make them sound like "babbling orphans beside a tomb."
Francis urged bishops to get close to their flock and help Mexicans "finally escape the raging waters that drown so many, either victims of the drug trade or those who stand before God with their hands drenched in blood, though with pockets filled with sordid money and their consciences deadened."
Francis ended his public activities Saturday at the Basilica of the Virgin of Guadalupe, which is the largest and most important Marian shrine in the world.
After delivering his homily, the pope sat silently in front of the image of the Virgin for nearly five minutes while the Mass continued. Later, he moved into a chamber behind the altar where the image is kept for nearly 30 minutes, fulfilling a wish to pray quietly before Mexico's patron saint.
"Just by looking at (the Virgin), Mexico can be understood completely," Francis said earlier.
The pope's five-day trip to the world's largest Spanish-speaking Catholic country is shining an uncomfortable spotlight on government and church shortcomings in dealing with social ills.
According to government statistics, about 46 percent of Mexicans live in poverty, including 10 percent in extreme poverty. Meanwhile, the homicide rate rose precipitously between 2006 and 2011, before declining somewhat for the next three years and then ticking up again in 2015. Since 2005, at least 1,554 women have disappeared in Mexico state, where Ecatepec is located, according to the National Observatory on Femicide.
On Saturday, vendors hawked pope T-shirts in Ecatepec as thousands of workers and security agents directed pilgrims and kept the peace.
Francis' schedule Sunday includes three popemobile motorcades and a visit to a pediatric hospital. Originally he also intended to meet with cultural figures, but that was nixed when the Vatican delayed his Ecatepec Mass by an hour so worshippers could arrive in the morning rather than camp out overnight in potentially freezing temperatures.
"The pope is coming to Ecatepec because it needs him and because the faith is reeling," said Petra Arqueta, a 62-year-old from Morelos who nonetheless spent a night waiting in line. "The poor and the working people are here, and this pope prefers to talk to the humble."