Miami had been a place where "all kinds of crazy things happen" and he didn't know if Boston would be "as wild and woolly". However, that quickly changed.
The day before he started work, the Globe ran a story by columnist Eileen McNamara about a priest, John Geoghan, who'd been accused of abusing 80 children. In it, a lawyer for the plaintiff claimed that Cardinal Law, the Archbishop of Boston, knew of the abuse, and yet had allowed the priest to be reassigned to different parishes.
"The response from the Church, via its lawyer, was that these were irresponsible, baseless charges," says Baron. "So you had duelling commentaries about these serious allegations."
What intrigued him most was that McNamara said the truth may never be known, because the internal Church documents that might reveal it were under seal and subject to a confidentiality order.
At his first editorial meeting, the following day, Baron proposed trying to get the seal lifted through legal channels. He then asked the paper's Spotlight team of investigative journalists to explore whether Geoghan represented a bigger problem.
The probe would bring the reporters and the paper up against the Catholic Church, whose buildings dominate the Boston skyline in the working-class areas where most victims came from, physically illustrating its influence over the life of the city. Baron, however, is not a man to be cowed.
As the editor of his high school newspaper in Florida, he refused to back down over a story that upset the administration. Since then, as well as the Catholic Church, he has stood up to the White House over stories about lapses in Secret Service coverage for the president, and resisted pressure not to publish confidential National Security Agency memos leaked by Edward Snowden.
Neither of his parents, who emigrated from Israel to the United States in the 1950s, was in journalism. But they had a keen interest in news about the public affairs of their adopted home. "As a matter of routine in our household, we'd read a local newspaper and watch the television news". And this clearly rubbed off on him.
At school, he was aware of "people of a certain status in life who felt that they were entitled and privileged", and says: "I think I've always been conscious of elites in society, and very leery of elites, frankly."
Today, he sees it as a "special obligation of the news media to hold powerful individuals, powerful institutions, accountable. Because my view is if we don't do it, nobody else will."
As a result of the movie, people have asked him why he went after the Catholic Church. The question irritates him. "I didn't decide to take on the Catholic Church," he says firmly. "I decided to pursue a story that was in front of us. It was a journalistic impulse. . . It became apparent to me, fairly quickly, that we had not pursued every possible channel for getting at the truth. And that's my job."
However, he did insist that they wouldn't publish until they had evidence of institutional malpractice. Simply reporting how many priests were involved would have struck people as sensational, he insists. For him, the more powerful questions concerned why they had been allowed to get away with the abuse for so long.
The facts uncovered were so damaging and so shocking that they didn't need to be sensationalised or conveyed with emotive language.
Baron and his team were expecting "blowback" when the first part of their (ultimately Pulitzer-winning) series of reports ran in 2002. "We actually stepped up on the switchboard because we were expecting a lot of criticism, and people to call and complain and accuse us of being anti-Catholic." Instead, as portrayed in the film, "there was an eerie silence".
"I think there was a strong feeling of betrayal amongst Catholics in Boston," offers Baron, "and they were able to feel that sense of betrayal especially acutely because we were able to put in front of them the actual internal Church documents that showed how the Church had deceived, had obstructed, and had ignored this problem for such a long period of time."
The pain that had been inflicted on children over many years was finally laid bare. Survivors now came forward in huge numbers to relate their stories, achieving what Baron sees as another key part of the "journalistic mission" - breaking the silence.
"I do think that we have to be especially attentive to people who are at the margins of our society, who don't have power, and who have not been given a voice," he says.
"One of the great lessons of this movie is that people who have been left voiceless can have very powerful things to say, and it's important that we listen to what they have to say. And at times act on it."
The message could hardly be more timely.
'Spotlight' is on general release
