A little-known Holocaust hero saved thousands, including a boy who became a University of Utah professor. Hundreds of Utah teen musicians will tell the story.

Daniel Mattis was 7 when his family narrowly escaped the Holocaust, leaving on the last train out of Brussels, Belgium, before Nazis bombed the tracks behind them.

The family made it to Bordeaux, France, where they were among tens of thousands of Jews and other refugees who got visas signed by Portuguese consul Aristides de Sousa Mendes — in defiance of a dictator’s order — in June 1940.

Mattis, now a University of Utah emeritus professor of physics, will be in the audience Saturday when the Utah Youth Orchestras and Ensembles present Neely Bruce’s “Circular 14: The Apotheosis of Aristides,” an oratorio dramatizing Sousa Mendes’ act of conscience. Salt Lake resident Ari Mendes, a grandson of the diplomat, also will be there.

The free concert at the Salt Lake Tabernacle, which also features hundreds of singers from the University of Utah and high schools statewide, coincides with the International Holocaust Day of Remembrance.

“It feels like a celestial thumbs-up,” bassist Dante Zubel, 17, who travels from Vernal weekly to rehearse with Utah Youth, said of the timing.

The State of Israel in 1966 recognized Sousa Mendes as Righteous Among the Nations, a distinction he shares with better-known Holocaust rescuers such as Oskar Schindler and Raoul Wallenberg.

Why isn’t his story as widely known?

Bruce and Utah Youth music director Barbara Scowcroft said one reason was Portuguese Prime Minister Antonio de Oliveira Salazar’s ruthless efficiency in erasing Sousa Mendes from history.

“That’s how fascism works,” Scowcroft said. “[Sousa Mendes] died in poverty in a Franciscan hospital.”

Sousa Mendes was stationed in Bordeaux in November 1939 when Salazar issued “Circular 14,” instructing diplomats not to assist refugees, particularly Russians, Eastern Europeans and Jews. Thousands of refugees funneled into Bordeaux, including Sousa Mendes’ friend Chaim Kruger, a Polish rabbi. Sousa Mendes offered to sign Kruger’s visa into Portugal, which was neutral politically during World War II. But the rabbi asked that the consul assist the other refugees.

“[Sousa Mendes] didn’t want people to suffer, but he didn’t want to disobey a direct order,” Bruce said.

As the story goes, “Sousa Mendes goes to his study and locks the door,” Mattis related. “Two, three days later he comes out and his hair has turned white. He says, ‘I will give visas to anyone who asks.’ The visa allows you to cross Spain.”

Sousa Mendes’ assistant, wife, children and Kruger helped process the papers, with some of them forging the diplomat’s signature. They worked day and night as Salazar’s secret police closed in, eventually moving their operation to Bayonne and then to a tiny border town.

It’s impossible to know exactly how many visas were signed, Bruce said, because only the first few hundred were registered. The secret police put the number at 40,000, but 30,000 is the generally accepted figure. Among those saved by Sousa Mendes were “Curious George” authors H.A. and Margret Rey, film director King Vidor and the family of artist Salvador Dalí. Actor Michel Gill, narrator of Saturday’s concert, is a son and grandson of visa recipients.

After getting their paperwork, the Mattis family took a train to Portugal with about 1,000 others, stopping only for fuel; no one could get on or off the train, and Mattis said he’ll never forget the faces of the starving people outside. After a month in the Portuguese town of Coimbra, the family took a three-week journey to Rio de Janeiro on a ship he described as “a tub.”

Mattis became a U.S. citizen after graduating from the Massachusetts Institute of Technology; he met Noemi Perelman, who also escaped the Holocaust as a child, on a return visit to Brussels, and they married in 1958. Their daughter, Olivia, a musicologist and historian, co-founded the Sousa Mendes Foundation in 2010.

She asked Bruce to set the story to music after a brief Facebook interaction. “It took me a matter of seconds to agree,” the composer said. He began researching the story right away. He started writing the music while on a tour of Sousa Mendes historical sites, organized by Olivia Mattis, in 2013.

Scowcroft and the Mattis family attended the premiere of a chamber version of the two-hour oratorio in Los Angeles two years ago. Saturday’s performance will be the first with a full orchestra.

“Even the young people were totally captivated,” Noemi Mattis said of the L.A. concert. “People had tears. Often contemporary music is an acquired taste. In this case, you will hear it and you will love it.”

Several members of the youth orchestra talked about the score during a recent break in rehearsal. Its vivid depiction of events, such as a series of eighth notes repeating over and over in the strings to represent the assembly line of signing and stamping documents, appealed to them.

Though the teen musicians had learned about other Holocaust heroes, Sousa Mendes’ story was new to them. “It teaches us both the kindness of humans and heroism when you least expect it,” said violinist Maya Miro Johnson, 16, of Salt Lake City.

“This type of story is an important educational experience that our young students need to have,” said Barlow Bradford, director of choirs at the U., who volunteered to conduct Saturday’s performance. “We cannot lose this kind of history if we intend to survive in the future.”