Former ad man David Shamoon did not capture Hollywood's attention overnight as a screenwriter. But now that he has it for "In Darkness," one of this year's Oscar nominees for Best Foreign Language Film, the Toronto-based screenwriter could see his first produced screenplay win one of Hollywood's top honours.

Inspired by true events, "In Darkness" tells the story of Leopold Socha, a sewer worker in the Nazi-occupied city of Lvov, Poland who risked his life to hide a group of Jews during the Second World War.

"People have come to me after seeing it in tears. Then they thank me. That's a good thing," Shamoon said Wednesday, appearing on CTV's Canada AM.

Shamoon first stumbled upon Socha's tale in 2003, after reading an article in a Toronto newspaper. That lucky find led Shamoon to the book "In the Sewers of Lvov," by Robert Marshall's book, which Shamoon would later adapt as a screenplay.

But Shamoon discovered that Socha was nothing like the selfless Swedish diplomat Raoul Wallenberg and other humanitarians who rescued Jews during the Second World War.

"He starts off a thief and is very much an opportunist," said the 64-year-old screenwriter.

Lured by their money, Socha agreed to shelter these hunted men, women and children from the Nazis in Lvov's labyrinthine sewers. In time, however, this unsavoury figure undergoes a deep personal transformation thanks to his charges and his dangerous task.

"This was his journey," said Shamoon.

"It's a very visceral movie. That's the way I see."

As part of the film's research, Shamoon, director Agnieszka Holland and producers Eric Jordan and Paul Stephens went into Lvov's sewers.

"We lasted for 45 minutes. It was the most terrifying experience I've ever had. These people lived in them for 14 months," said Shamoon.

That eye-opening experience, coupled with Holland's masterful direction, helped to stoke the gripping sense of terror and moral outrage that drives this movie.

That intensity was heightened by Holland's insistence on shooting "In Darkness" in the story's original languages and not in English.

Holland, the director of 1990's Oscar-nominated film "Europa, Europa," worried very deeply that the film's powerful story would be marred by a bunch of Hollywood actors delivering bad accents.

"She finally said if you want me to direct this it has to be in the original languages," he said.

Holland eventually got her way.

"We really wanted her to direct," said Shamoon.

Her request made sense to Shamoom, who identified with this harrowing story on a personal level.

Shamoon's parents were Iraqi Jews. In 1941, they sought refuge in India, where Shamoon and his brothers were born. The family later moved to Iran where Shamoon spent his teenage years.

In 1970, Shamoon moved to Canada after studying advertising in the United States.

Thanks to Polish backers, "In Darkness" was eventually filmed and went on to earn critical praise on the 2011 film festival circuit.

Even so, "In Darkness" will have a fight on its hands at this year's Academy Awards.

Other nominees include Canada's official entry "Monsieur Lazhar," Belgium's "Bullhead," Israel's "Footnote," and Iran's "A Separation, which won the Golden Globe for Best Foreign Language film earlier this month.

Win or lose, Shamoon is content that "In Darkness" has passed the test with one real-life survivor from Socha's story.

"Eric Jordan and I flew down to New York to screen a rough-cut for her," said Shamoon.

"I was nervous. What if she didn't like it?" he said.

After the screening, the woman was bathed in tears.

"‘That's how it really was,' she told me," said Shamoon.

The 84th Academy Awards will air on Sunday, Feb. 26 on CTV.