Vatican correspondent Nicole Winfield sensed a potentially explosive development in Chile's long-running sex abuse and cover-up scandal when she noticed a cryptic tweet from a former member of the Pope Francis' abuse advisory board.

Board member Marie Collins had tweeted that Francis was well aware that victims of Chile's most infamous predator priest had placed Bishop Juan Barros at the scene of their abuse, since she herself had been involved in relaying their concerns to him.

Intrigued and sensing an important twist in a story that AP has already dominated, Winfield and Santiago correspondent Eva Vergara kicked off an extraordinary effort that would culminate in the beat of the week – a three-day, multinational, cross-format papal fact-check that prompted published calls for the pope to come clean about a scandal that now threatens his legacy.

It involved a Paris airport stakeout by senior TV producer Jeff Schaeffer, a missed Super Bowl party hosted by Philadelphia-based TV producer Yvonne Lee and a surreal TV interview conducted by AP reporters on three continents.

All over the course of one frantic weekend.

A brief recap: A Vatican court in 2010 convicted a prominent Chilean priest, the Rev. Fernando Karadima, of sexually and psychologically abusing minors. Barros was a Karadima protege who went on to have a successful career as a bishop.

After the Karadima scandal exploded, Chile's bishops recommended Barros and two other Karadima-trained bishops resign and take a year sabbatical, to calm the waters.

Francis, though, refused to accept the resignations because he said he had no "evidence" that they had done anything wrong. He named Barros to head the diocese of Osorno, in southern Chile, where priests and lay faithful have refused to accept him.

During his tumultuous in-flight press conference home from South America last month, Francis said he could not remove Barros because he had never heard from any victims about the bishop’s behavior.

Which is why Collins' tweet was pivotal.

Collins revealed to Winfield that during an emergency summit of the pope's sex abuse advisory commission in April 2015, she handed over a letter to the pope’s top adviser, Cardinal Sean O’Malley. The letter from Karadima victim Juan Carlos Cruz concerned Barros; it was intended for the pope.

Enter Vergara, who has cultivated a years-long personal relationship with Cruz over the course of her coverage of the Karadima affair.

She obtained the letter from Cruz, and it was heartbreaking: a plea for help from Francis, written in his native Spanish, to finally listen to him. The eight-page letter described in detail the abuse Cruz suffered at the hands of Karadima, and accused Barros of witnessing it, ignoring it and covering it up.

The letter called into question Francis' assertion that he had never heard from victims about Barros, and had no evidence of wrongdoing.

But did it ever get into his hands?

Winfield and Vergara knew that tracing the chain of custody of the letter would be crucial, and Collins offered up two links.

She told Winfield that O'Malley had assured her that he had given it to the pope and raised the issue with him. And she provided visual proof that it had at least gotten as far as O'Malley: A photo of her handing the letter over to O'Malley that she had asked a fellow commission member, Catherine Bonnet, to take so she could send it to Cruz.

The photo was crucial to telling the story, and Winfield set about securing authorization to use it from Bonnet, who also agreed to go on camera to describe the moment of the handoff.

Bonnet, though, was travelling from San Diego to Paris on a more than 24-hour odyssey.

Enter Schaeffer, who kept in touch with Bonnet by texts during her layovers and tracked her hours-delayed flight online, so that he could meet up with her at Charles de Gaulle to conduct the interview. Paris photographer Michel Euler joined him in scouting the location that would be appropriate for such a sensitive interview.

Once set up, Schaeffer waited outside the baggage carousel with a sign saying "Catherine - AP" in big letters so Bonnet would recognize him.

Lee rushed from her Super Bowl party to shoot video at the victim's Philadelphia home, where she called Winfield, who was waiting at home in Rome to conduct the phone interview. Winfield had Vergara on WhatsApp, completing the three-continent interview.

Next, the attention shifted to trying to get Cruz on camera. Cruz was home in Philadelphia, about to go to a movie when Vergara asked him to stay put and wait for an AP film crew.

Enter Lee, who was preparing for a 6 p.m. Super Bowl watch party at her house, a historic occasion given Philadelphia had been waiting more than a half-century for a championship.

Called upon to help out, videographer Lee said she was preparing for a party. But she dropped everything after learning the details.

She hustled to the office to get her equipment and arrived at Cruz's apartment, only to realize that her tripod plate was missing. Lee improvised, using a high chair and a stack of books.

As soon as she was set up, she called Winfield, who was at home in Rome on a Sunday night in her pajamas, waiting to conduct the interview by speaker phone. Winfield had Vergara online in a WhatsApp chat and relayed what was happening, completing the three-continent interview.

Cruz revealed that O'Malley had assured him that he had delivered the letter, completing the chain of custody with two named sources. (For the record, Lee made it to her party. As her guests watched the Eagles win, she edited and transcribed the interview, and sent the file to the BNC before the game ended.)

With all the parts in place, the story rolled out on Monday morning. The New York Times credited AP, as did numerous Italian media as well as France's Le Figaro, Spain's El Pais and Chile's major newspapers. Teletrax reported extraordinary video play.

Commentary followed, predicting that Francis' legacy would be forever tarnished: "Pope Francis' failure to address the abuse allegations jeopardizes his papacy," read an opinion piece in Time magazine.

For teamwork that spanned the globe, in service of a story of immense global interest, Winfield, Vergara, Schaeffer and Lee share this week’s $500 prize.