Benedict Cumberbatch, left, and Chiwetel Ejiofor in a scene from...

Benedict Cumberbatch, left, and Chiwetel Ejiofor in a scene from "12 Years a Slave." The film, by director Steve McQueen, is being hailed a masterpiece and a certain Oscar heavyweight. It opens Oct. 18. Credit: AP

'I didn't know I didn't know these things about slavery," says Kenyan actress Lupita Nyong'o, whose big-screen debut -- director Steve McQueen's "12 Years a Slave" -- is likely to have audiences all over America saying precisely the same thing.

Destined to rule at this year's awards season, and to rattle audiences with its unyielding portrait of America's original sin, "12 Years" is that uncommon Hollywood creature, a bona fide morality tale with all-star actors. They include Michael Fassbender, Alfre Woodard, Sarah Paulson, Brad Pitt, Paul Giamatti, Benedict Cumberbatch and star Chiwetel Ejiofor, who said he didn't understand why he'd never heard the story of Solomon Northup, a free-born black man and musician from Saratoga Springs, who, in 1841, was duped into traveling south, abducted and sold into slavery. The film opens Friday in limited release.

It's one of the great untold stories in American history -- even though Northup himself told it in the memoir "Twelve Years a Slave," published in 1853.

"Steve sent me the script, about this extraordinary tale, and I was surprised I didn't know it," said Ejiofor, the London-born actor who has appeared in "Salt," "Red Belt," "Talk to Me" and "Inside Man," among others. "And I was surprised again when reading the autobiography -- and struck by the responsibility of telling his story, a story from so deep inside the slave experience. Rather than a responsibility, it became a privilege."

Fassbender, the Irish actor who has made his reputation in movies by McQueen -- playing imprisoned IRA striker Bobby Sands in "Hunger" (2008) and a sex-addicted New Yorker in "Shame" (2011) -- echoed Ejiofor's bewilderment.

"It's such an incredible story, and it's incredible that I hadn't heard anything about it," Fassbender said in New York. "Of course, when Steve said he wanted to make a movie about slavery, it seemed pretty obvious: He always seems ready to tackle the elephant in the room. Several months later, I got the script and wasn't sure what part he had in mind for me. But I was hoping it was Epps."

Edwin Epps, on whose plantation Solomon does much of his suffering, is in love with one of his slaves -- Patsey, played by Nyong'o. Her treatment is so savage, audiences will certainly be rattled, possibly offended, inevitably disturbed. But McQueen's understated yet unmistakable point is that no one involved was unscathed by the horrors of slavery.

"Giving out pain to everybody every day has an effect on everyone," Fassbender said. "For me, it was important for the audience, when they see Epps, to maybe say, 'I recognize something of myself in there.' He's a guy they cannot hold at arm's length from themselves."

Neither, of course, is Northup, whom Ejiofor admits he didn't quite grasp at first.

"The first time I read the script, I didn't see Solomon in the story," he said. "I saw a man and the story as a whole thing, an amazing story of a man trying to get back to his family. And it was only really when I was reading the biography that it struck me that it was specifically about this individual, who has a very fascinating way of looking at the world."

Northup, said Ejiofor, was in a battle for his own mind. "And anything that's not going to help him, he cuts loose. Hatred isn't going to help him. He's intent on remaining sane and not breaking, and I think he was an extraordinary person."

Similar things are being said by the actors about their director, the 43-year-old British installation artist, video-maker, Cannes honoree (for "Hunger") and recipient of the Tuner Prize, given annually by London's Tate Museum. He was the main reason, Woodard said, that she got involved in the film.

"For me, it was all Steve McQueen," said the actress. "I was so excited, in this way when you say, 'Oh my God, here's a new filmmaker with a voice and a vision and artistic ability.' I saw 'Hunger' and then 'Shame' -- I was campaigning for that because I thought it was the best picture the year it came out. And then came the moment I got a call from the agents saying, 'Steve McQueen would like you to be in his film, he wants you for this picture,' and I said, 'Whatever, yes!'"

For Ejiofor, whose parents are Nigerian, there was McQueen, as well as a personal connection to "12 Years a Slave."

"I was in Savannah, Georgia," the actor recalled, "which historically is sort of an untouched and pristine place. And there are these two tours you can go on, the tour of Savannah, and the black tour of Savannah."

He took the latter, and described a sort of little alcove which "back in the day was used for slaves who'd just gotten off the boats, with these cast-iron gates that would slam shut on them. With a walkway above that would give the people of Savannah an opportunity to see who came off the boat, and who they might like to buy."

He saw a series of bolts in the walls -- "probably there for hundreds of years" -- and asked what they were for.

"The tour guide said, 'Oh, those were for the Igbos,'" meaning the tribe from southern Nigeria. "I said, 'I'm an Igbo ...' and I was suddenly very connected to this experience.

"But slavery is an international story," Ejiofor added. "Everyone in the African diaspora is connected to this, and telling the story, which says so much about human respect and human dignity, has an impact wider than any one country."

The TV miniseries "Roots," based on the Alex Haley novel, is probably still the best remembered slavery-themed effort in American entertainment -- the airing of the final episode in January 1977, is still No. 3 on the all-time Nielsen's ratings list. On the big screen, the not-so-feel-good subject has left a sometimes memorable, sometimes sketchy legacy, as exemplified by the following:

SUBSCRIBE

Unlimited Digital AccessOnly 25¢for 6 months

ACT NOWSALE ENDS SOON | CANCEL ANYTIME