Right Now: The pope has landed in village of Knock to pray at a revered shrine.

On the second day of a difficult mission to win back the confidence of Irish Catholics, Pope Francis awoke on Sunday to a bombshell attack from within his own citadel.

A former top-ranking Vatican official released a 7,000-word letter asserting that the pontiff had known about the abuses of a now-disgraced American prelate, Cardinal Theodore McCarrick, years before they became public.

Carlo Maria Viganò, a right-wing critic of Francis and a former Apostolic Nuncio to the United States, claimed that the pope had failed to punish Cardinal McCarrick, who was suspended in June following allegations that he coerced seminarians into sexual relationships. He was also found to have abused a teenage altar boy 47 years ago, when he was a priest in New York.

In the letter, published by the National Catholic Register and Lifesite News, publications critical of Francis, the archbishop called on the pope to resign.

“In this extremely dramatic moment for the universal Church,” the archbishop wrote, “he must acknowledge his mistakes and, in keeping with the proclaimed principle of zero tolerance, Pope Francis must be the first to set an example for cardinals and bishops who covered up McCarrick’s abuses and resign with all of them.”

The Vatican did not immediately respond to a request for comment.

The archbishop’s startling accusation will not come as a complete surprise to Vatican watchers, since he is part of a conservative camp that blames liberals, like the pope, for allowing homosexuality in the church. But it further complicates Francis’ efforts to persuade Irish Catholics that the church is ready to confront its legacy of concealing sexual abuse.

• After the pope’s meeting with survivors of abuse on Saturday, Francis traveled on Sunday to the west of Ireland to visit a shrine in the village of Knock.

• Francis again addressed the issue of child sexual abuse by members of the Catholic Church in a speech at Knock Shrine,” begging “for the Lord’s forgiveness.”

• Vigils were expected across the country, including one in Tuam, where the remains of hundreds of children were found buried in an abandoned septic system of a Catholic-run home for unmarried mothers.

• Here are highlights of the pope’s visit to Ireland from Saturday.

• The New York Times will have live coverage from Ireland throughout the pope’s two-day visit.

Francis headed on Sunday to the tiny, hilly village of Knock, home to fewer than 1,000 people. Knock has served as an engine of faith for the Catholic Church since 1879, when a group of townspeople reported seeing apparitions of the Virgin Mary and other members of the holy family.

Some 45,000 of the country’s Catholic pilgrims made their way here on Sunday, through heavy traffic and pouring rain. It is telling that Francis used his time here to beg for God’s forgiveness.

Under drizzly, misty skies and the soothing sound of Ave Maria, silent onlookers surrounded the Knock Shrine, which went into a lockdown at 9:20 a.m., a few minutes before the plane carrying Francis touched down at Ireland West airport.

“The pope has arrived,” the choir announced, as a screen showed his descent from the steps of the plane. Audience members cheered, clapped and said, “God Bless him.”

At the shrine, the pope declared: “None of us can fail to be moved by the stories of young people who suffered abuse, were robbed of their innocence, who were taken from their mothers, and left scarred by painful memories.”

“This open wound challenges us to be firm and decisive in the pursuit of truth and justice. I beg the Lord’s forgiveness for these sins and for the scandal and betrayal felt by so many others in God’s family.”

Francis prayed at the shrine, asking the Virgin Mary to heal those who have been abused.

John Paul II also prayed here on the last papal visit to Ireland, in 1979. After that visit, the local priest, Monsignor James Horan, drew widespread mockery for vowing to build an airport in the tiny village.

“Now don’t tell anybody,” he told a television crew. “We’ve no money but we’re hoping to get it next week or the week after.”

The airport was competed in 1986, and, in its way, became a symbol of the power of the Irish church.

The village had prepared feverishly for this papal visit. More than 50,000 flowers were planted, buildings along the main road were repainted, and every bed-and-breakfast in town — including ones called the Lamb of God, Divine Mercy and the House of Eden — had been fully booked by Friday.

“It was very emotional when we saw the pope in 1979,” said Tina Stenson-Cunningham, 63, holding onto a railing by the road where the Popemobile was expected to pass through. “But now we’ve experienced more of life, it’s more meaningful, more spiritual,” she said.

— Iliana Magra and Jason Horowitz

On Saturday, in a 90-minute meeting with survivors, the pontiff forcefully expressed his disgust with the church’s history of sexual abuse, condemning “corruption and cover up within the church as ‘caca,’” using a Spanish word for excrement.

But his efforts, wrapped in the pomp and celebrity of a two-day visit, left some of his Irish audience cold.

“Usually, when someone comes to visit, you get to know them better,” wrote Fintan O’Toole in The Irish Times. “How can someone have such a warm and human touch on one hand and be so terribly out of touch on the other?”

Ireland has transformed itself over the past decade, throwing off the teachings of the Roman Catholic Church in a series of momentous steps following revelations not just of clerical sexual abuse, but also of the virtual enslavement of unwed mothers in so-called Magdalene laundries and other grim church-run institutions, and forced the adoptions of many of the children.

Same-sex marriage was approved in Ireland in 2015, one of the world’s most restrictive abortion laws was scrapped there in May, and the pope was welcomed on Saturday by the country’s first gay prime minister.

Some have called for new zero-tolerance procedures, like the creation of a tribunal to judge bishops who do not appropriately handle accusations of sexual abuse. As Tony Kelly, 58, a bar manager in Dublin, said on Saturday, “People are looking more for actions rather than words.”

But so far, the leader of the world’s 1.2 billion Catholics has given no hint that groundbreaking new practices are imminent.

— Jason Horowitz

The pope’s visit to Knock offers countless reminders — like his recitation of the Angelus prayer at the shrine — that for all the changes in Ireland, Catholicism remains deeply rooted in the country.

The Angelus — a Catholic devotion commemorating the Incarnation — is broadcast twice each day by Ireland’s public broadcaster, RTE, and the shrine draws crowds of visitors.

Until the 1970s, the Irish Constitution recognized “the special position” of the Roman Catholic Church, and the Constitution says, “The state acknowledges that the homage of public worship is due to Almighty God.”

Most schools in Ireland are government-funded but privately run, and in most cases that means run by the church — more than 90 percent of primary schools are Catholic.

Church schools are permitted to give preference in admissions to Catholic children, which has prompted some non-Catholic parents to have their children baptized into the church.

The archbishop of Dublin, Diarmuid Martin, has long pushed for the church to divest itself of many of its schools, but the religious orders that control them have resisted.

Ireland’s 2016 census found that 78 percent of residents considered themselves Roman Catholic — down from 94 percent in 1971, comparable to the level of Catholic identification in Italy and higher than the levels found in Spain and France.

— Richard Pérez-Peña

Aerial footage so far has shown fewer people than expected on the streets to greet Francis as he has made his way around in his Popemobile, for example, to St. Mary’s Pro-Cathedral from Dublin Castle on Saturday.

Television footage showed throngs of fans at street corners, but crowds quickly turned into single files alongside the road, cheering as the pope approached.

Fewer than 600,000 are expected to attend the open-air Mass on Sunday, less than half the number that turned out to watch John Paul II in 1979, when about 1.25 million gathered to see him.

It was unclear whether a protest called “Say Nope to the Pope,” which encouraged people to snap up free tickets and then skip the events, was having an effect.

— Kimiko de Freytas-Tamura

Matt Talbot died in obscurity 93 years ago, having drawn little attention after living a quiet existence of modest means and hard labor. But on Saturday, the leader of the world’s Catholics stopped at Our Lady of Lourdes Church in Dublin to pray before relics of Talbot, who is far better known in death than he was in life.

Talbot, an alcoholic Dubliner known as the “Holy Drinker,” overcame his addiction with the help of a priest and became deeply religious. His story spread rapidly after he died. Substance abuse clinics around the world are named for him, as is a bridge in Dublin with a statue of him nearby.

Already an unofficial patron saint to those struggling to stay sober, he may be granted official status. The church gave him the title “venerated” in the 1970s, a step toward canonization.

One of 12 children born to a poor family, with a father who was a violent alcoholic, Talbot began drinking heavily at age 12 and became so addicted that he once pawned his boots to buy a pint at a pub. At 27, he swore never to touch alcohol again — a vow he kept until his death, 42 years later.

“Never go too hard on the man who can’t give up drink,” he is quoted as having said. “It is as hard to give up drink as it is to raise the dead to life again.”

— Kimiko de Freytas-Tamura