The Great Debaters on Oprah

In the film, Forest plays James Farmer Jr., a role he says brought him closer to his grandfather. Fifty years ago, Forest says his grandfather founded a church in the same part of the South where the film is set.

"It was an opportunity to get a chance to try to pay homage to this kind of a man," he says. "There's a sternness. There's a certain way of raising kids because of the environment and what can happen to them. It was a great chance to get to do that."

Denzel says he told Forest not to make his character "too nice," because he was from a generation of African-American fathers who were strict with their children. This parenting method was adopted, in part, to protect children from the hostile racial climate of the 1930s.

"It's love but it's different," Forest says. "As you can see in the movie, if you take the wrong step, you know, you can die."

In one scene, Denzel says Forest captures this intensity without saying a word. He simply gives the young man playing his son a look. "This guy can act right here," Denzel says.