TORONTO -- Casting the determined octogenarian who takes on the Austrian government in the film "Woman in Gold" required a fierce actress. That led director Simon Curtis to Oscar-winner Helen Mirren.

In looking for someone to play the younger version of that tenacious woman, Maria Altmann, for flashback scenes, he was hoping to find an actress who could tackle German dialogue. That led him to Canadian TV star Tatiana Maslany.

"It was one of the happiest days of my life when I met her because, A) she's an incredible actress and B) she spoke German," says Curtis during a recent stop in Toronto to promote the film.

"It was a film about identity and part of that identity is language."

That the versatile Maslany proved adept at handling her German lines should be of little surprise to fans of her acclaimed Space series "Orphan Black," in which she tackles a myriad of cloned characters, including the short-lived German clone Katja Obinger.

The Regina-bred actress, whose grandparents are German, says this was the first time she'd tackled a role exclusively in another language. But she was excited to try.

"My mom taught it to me when I was a baby so it's there in my head somewhere, you know," says Maslany, who also speaks French. "It's definitely not something I speak on a regular basis so it was a challenge."

"Woman in Gold" traces the true story of Altmann's legal battle to retrieve family possessions seized by the Nazis in Vienna during the Second World War.

Those possessions include Gustav Klimt's celebrated 1907 painting, "Portrait of Adele Bloch-Bauer I," which features Altmann's aunt posing like an Egyptian queen, adorned in gold and jewels. The masterpiece makes its way to the national Belvedere museum in Vienna, where it is regarded as the "Mona Lisa" of Austria.

Mirren plays the aging Altmann as she pursues justice some 60 years later with the help of inexperienced young lawyer Randy Schoenberg, played by Vancouver-bred Ryan Reynolds.

The real Schoenberg -- the grandson of the Austrian composers Arnold Schoenberg and Eric Zeisl -- was thrilled to be portrayed by People magazine's 2010 "Sexiest Man Alive," chuckles Curtis.

"The chemistry between Helen Mirren and Ryan Reynolds was so exciting to see," he adds. "A lot of the comedy and humanity of the film comes from that relationship."

Principally, the story is set in Los Angeles in the recent past (with English dialogue), with Altmann and Schoenberg embarking on an against-all-odds campaign all the way to the U.S. Supreme Court. Throughout their fight, the story jumps back in time to Vienna during the war, when a young Altmann makes the difficult decision to leave her family forever.

Even though they don't share screen-time, Maslany says she was grateful to discuss the role with Mirren: "She really gave me so much ownership over the character and just said, 'Make her yours and don't try to be me."'

Curtis says both actresses watched videos of Altmann to nail down complementary performances.

"It's amazing, through the magic of cinema, how credible it is that they're both playing the same woman," says the director, who also brought Marilyn Monroe to life in the 2011 film, "My Week With Marilyn."

Then there was the matter of casting the golden painting itself.

While Klimt took years to complete his glittering opus, Curtis had weeks to find two versions to film -- one work-in-progress and another finished.

"We took it for granted (that) we'd be able to recreate it rather stupidly because Klimt took three years to paint it. But we found an amazing man in London who did a brilliant job," he says.

The real Klimt is at the Neue Galerie in New York. Where is the reproduction?

"I'm not telling," Curtis fires back, chuckling.

Eventually it will likely be destroyed, he allows. Maybe.

"Someone told me that if it doesn't have the signature on it, it's not actually a recreation of the painting," he says. "And in any case, since the real painting is very much in a very secure, very public place, it would be hard to convince anyone that it was the real one."

"Woman in Gold" opens Friday in Toronto, Vancouver, Calgary, Edmonton, Ottawa, Victoria, Winnipeg, and Halifax before heading to other markets.