Holding prominent officials accountable is one of the main missions of journalism, even if it is uncomfortable at times. AP’s Nicole Winfield did just that, politely but firmly pressing Pope Francis on his knowledge of a sexual abuse scandal that has clouded his appointment of a Chilean bishop in 2015 and cast doubt about his commitment to fighting the problem. Along with AP Santiago correspondent Eva Vergara, Winfield shares Beat of the Week.

Vergara got the first part of the scoop for AP. She knew a letter she had spent months tracking down was toxic to Francis, to his upcoming trip to Chile, and to the Chilean bishop appointed by Francis and accused of covering up for the country's most notorious pedophile priest.

Ap 18011807539957 Letter

A copy of a confidential Jan. 31, 2015 letter from Pope Francis obtained by AP's Eva Vergara, with details of the behind-the-scenes maneuvering to deal with prelates connected to Chile’s most notorious pedophile priest, Rev. Fernando Karadima.

AP Photo

When she finally got ahold of it, she took measures to protect her source lest anyone start investigating who gave it to her. She donned latex gloves when she touched it to photograph it, then wiped it clean to remove any trace that it was ever in her hands.

The revelations in that letter from Francis to the executive committee of the Chilean bishops' conference about the appointment of Bishop Juan Barros became a major part of Francis' just-concluded trip to Chile and Peru. The scandal and Francis' subsequent accusations of slander against abuse victims dominated coverage. It led to Francis trying to explain himself under tough questioning by Winfield on an extraordinary in-flight press conference on his way home.

The letter showed that Francis knew that Barros was accused of complicity in covering up the sexual abuse by Rev. Fernando Karadima, but appointed Barros bishop anyway. It also revealed that the Vatican at one point was prepared to sack Barros and two other Karadima-trained bishops but didn't. It became front-page news in major Chilean media and was picked up widely internationally. The most-read Vatican commentator, Sandro Magister, wrote an entire column about it.

The letter's importance, and AP's dominance of the story, only grew once the trip got under way. Francis opened his Chile trip by issuing an apology to all victims of sex abuse, and he met with a small group of survivors on his first full day in Santiago. But a few days later, Francis was asked by a Chilean journalist specifically about the Barros appointment, which had outraged Chileans ever since it was announced in 2015.

Francis' comments caused more consternation: "The day they bring me proof against Bishop Barros, I'll speak," Francis said. "There is not one shred of proof against him. It's all calumny. Is that clear?"

Winfield, who was part of the Vatican's traveling press pool, sensed the gravity of Francis' words: The pope was accusing sex abuse victims of slander. Her story that night – filed after an incredible day in which the pope married two flight attendants – was widely picked up.

The Boston Globe, which broke the sex abuse story in the U.S. in 2002, linked to Winfield’s story in a blistering piece by columnist Kevin Cullen titled "Pope Francis, Company Man."

Winfield then filed even bigger news: Francis' top sex abuse adviser, Cardinal Sean O'Malley, had publicly chastised the pope for his comments. O'Malley said Francis' words had been the source of "great pain" to victims, made them feel abandoned and left in "discredited exile."

By the time the flight home came around, Francis knew he had to address the issue.

"One of you came to me and showed me a letter I wrote several years ago..." Francis began, referring to Winfield's request for comment two weeks earlier about the letter – a request that had been met with silence from the Vatican.

When it was her time to ask a question, Winfield then questioned Francis on his words about the Barros accusers, his partial apology earlier in the press conference, and O'Malley's rebuke.

In a remarkable exchange that earned her a warning, Winfield told the pope that the accusers were abuse victims, not just any-old dissidents.

Winfield told the pope that victims weren't so upset that he demanded to see proof of their claims but that he had accused them of slander. In a remarkable back-and-forth that earned her a warning from the Vatican spokesman, Winfield told the pope that the Barros accusers were abuse victims, not just any-old dissidents, as he seemed to think.

Pope: "If I say 'you stole something, you stole something,' I'm slandering you because I don't have evidence."

Winfield: "But these are victims saying this!"

Pope: "But I didn't hear from any victim of Barros."

Winfield: "There are victims. There are victims. They're Karadima's victims. They say Barros was there."

Pope: "They didn't come forward. They didn't give evidence for the judgment."

Which was not accurate, as Winfield wrote in her story filed after the plane landed in Rome. Victim Juan Carlos Cruz testified to Chilean prosecutors that Barros had witnessed Karadima's abuse.

The AP’s trip coverage was widely praised. Winfield received emails from abuse victims and even Mitchell Garabedian, the lawyer (portrayed by Stanley Tucci in the movie "Spotlight") who helped bring the U.S. abuse scandal to light.

"Thank you for your reporting," he wrote.

For Winfield’s extraordinary conversation with the pope and the letter that launched it all, Winfield and Vergara share this week’s $500 prize.