05/10/2013 02:22 pm ET Updated Jul 10, 2013

Finding Out What Maisie Knew From the Adults Around Her

Acting is about being in the moment and discovering the character within it.

But before emotional scenes in What Maisie Knew, Julianne Moore would often warn the other actor in the scene, "Now I'm going to cry here -- but I'm not really sad, I'm just acting."

And her co-star, then-six-year-old Onata Aprile, would smile, say, "OK," and knock the scene out of the park.

Aprile is the Maisie in What Maisie Knew, an adaptation of the Henry James novel, told in a modern milieu by directors David Siegel and Scott McGehee. Maisie is the young daughter of rock singer Susanna (Moore) and traveling businessman Beale (Steve Coogan), who becomes the pawn in their bitter divorce, as they battle over their daughter without really wanting custody.

"She was this very bright, present and trusting little girl," Moore says of Aprile. "She had a great sense of humor."

Aprile is, in fact, at the center of the film as Maisie, in an almost eerily natural, watchful performance. She always seems to be in the camera's focus, while the marital squabbles and romantic entanglements explode in the background. Which is a lot to put on a young actress.

"I've worked with kids before but this whole movie revolved around this little girl," says Alexander Skarsgard, who plays the amiable and caring bartender who marries Susanna after she divorces Beale, becoming Maisie's de facto caregiver and stepparent. "The movie won't work if you have the wrong girl."

Skarsgard spends a large chunk of his time in the film interacting with Aprile, as her mother abandons her to his care while she leaves for a rock'n'roll tour. When he was offered the role, he was concerned that the chemistry be right between him and whoever the young actress would be. The Swedish actor saw video of Aprile, then flew to New York from Los Angeles to meet his would-be costar.

"I remember heading over there, thinking, 'I hope there's chemistry,' because you can't fake that -- it has to be real," he says. "But I got there and after about three seconds, I wasn't worried. She had this phenomenal energy. She's so alive and present and real. She can't lie."

The film, which was one of the top-grossing independent films when it opened last weekend, transposes James' tale of 1890s England to 21st century Manhattan, but doesn't lose the essential narcissism of Susanna and Beale.

"Narcissists -- that's exactly what they are," Moore says. "They're in a struggle over the child. Neither of them want custody - but both of them want to win."

Maisie, meanwhile, seems to be the only one who sees things clearly. And she sees everything.

"She does notice things," Moore says. "Susanna tells Maisie, 'I used to be just like you.' Because, to me, that harked back to a mother that ignored Susanna, and her vowing to be a better mother to her own child. Instead, she's what she is. And that's the tragedy."

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