On Movies | The up-and-coming Affleck

TORONTO - Don't underestimate

Casey Affleck

, the reedy-voiced, baby-faced actor, who is younger brother to

Ben

. Like the character he plays in

Gone Baby Gone

- the Boston-based kidnapping thriller opening Friday - the first impression Affleck makes is of someone a little callow, maybe, lacking heft. But by the time this hard-boiled mystery, with its sorry smackhead moms, its crooked cops, its low-life Beantown thugs, is over, Affleck's Patrick Kenzie has proved himself tougher than most.

Same goes for Affleck's portrait of Robert Ford, a boyish, stammering sidewinder who joins up with the outlaw hero Jesse James in the title-says-it-all The Assassination of Jesse James by the Coward Robert Ford. Affleck, with an apologetic, snaggletoothed smile, almost steals the loping, picturesque western - playing now in area theaters - out from under Brad Pitt.

"Casey's good, real good," says Pitt, who took the job as Jesse James. "It's an amazing performance."

In a hotel room on the eve of The Assassination of Jesse James' premiere at the Toronto International Film Festival, Affleck, 32, riffled through a festival program guide ("Heard anything about this new Peter Greenaway?") and fielded questions about his twin pics - pics that already have Variety enthusing that Affleck "shows low-key but potent acting chops to be reckoned with."

"I'm just so happy to be in something I really like," he says quietly, matter-of-factly. "It's not often that you even get to read a script that you really like, let alone actually be in the movie. And for me to be able to say that now about two movies at the same time - well, it's been something special for me."

Affleck shot Assassination of Jesse James, based on the novel by Ron Hansen, adapted by director Andrew Dominik, a year and a half ago, in the woods and prairies of Calgary, Alberta (subbing for 1880s Missouri). It's a meticulously detailed production, right down to the buttons on the cast's long johns.

"The movie was rehearsed in Andrew's mind for no less than five years," says Affleck about his director, a New Zealander who introduced Eric Bana to the world in the brutal Down Under character study Chopper.

"I've never seen a movie so well prepared," Affleck says of the elegiac western. "Andrew put everything of himself into the movie. When we showed up for the standard two-week rehearsal period, every single detail had been designed, every stitch of clothing had been scrutinized."

So Affleck, Pitt and cohorts Sam Shepard, Sam Rockwell and Paul Schneider practiced their lines, their riding skills, how to handle their six-shooters.

"These guys, they didn't have to be marksmen. They're not CIA operatives," Affleck says. "They are guys who often had no ammunition, they had bad guns - so I was as good as some of them probably were in real life, back in those days. You just pick up the gun, you aim and shoot.

"As for the horses - I love horses. I'm not sure horses love me. But I had a great time getting to ride a little bit better. It was cool."

Much has been made about the parallels between The Assassination of Jesse James - with its pop-cult cover boy, Jesse James, worshipped by fans and stalked by the press - and the modern-day celebrity culture that has made Brangelina a household name.

Affleck's character, Robert Ford, is, in a certain light, a kind of Mark David Chapman - a serious and seriously off-kilter fanboy, trying to get up close and personal with his idol.

"I think that there are some surface - maybe slightly deeper than surface - parallels to contemporary celebrity culture," Affleck acknowledges, hastening to add that "it wasn't something I focused on in making the movie.

"Robert Ford never felt like a stalker to me. It was just somebody who had a different sense of himself than the rest of the world had of him, and that really bothered him. He was sort of relentless, fearless, in his pursuit of the things that he wanted. And when he got them, they were different than what he thought they would be. That was the central thrust of the character for me. It was never really so much about like, 'Oh, I'm stalking this guy.' "

In Gone Baby Gone, which was adapted from the Dennis Lehane mystery by Ben Affleck and Aaron Stockard - and then directed by Ben Affleck, making a confident behind-the-camera bow - Casey is kind of a working-class Beantown Nick Charles to Michelle Monaghan's Nora. The private-eye duo, who work together, live together and sleep together, get hired on an ugly case about a missing 4-year-old girl. Morgan Freeman and Ed Harris are two of the Boston cops pursuing their own investigation. The film, shot in some hardscrabble Boston neighborhoods, gets fiercely violent, and so, too, does its star.

"We shot Gone Baby Gone about six months after Jesse James," says the actor, who lives in Los Angeles now, but grew up with the Affleck clan in and around Boston. His mother, who still lives there, was a teacher. His dad was a drug counselor, a mechanic, a bartender, an actor.

"It's a big advantage, playing a role in the place where you grew up, surrounded by the kind of people you grew up with," Affleck says. "The accent, the attitudes, all of that was just totally familiar."

About his brother, Casey says, "I'm really proud of what Ben did, I think he did a great job directing. He's a natural leader, and people really want to follow him, but he also, like any good leader, knows when to follow himself. He's very collaborative."

And Affleck is proud that his brother's directing debut is also a celebration of their hometown.

"Having grown up there, Ben had a firm grasp on the atmosphere, the environment there. And I think that that comes across. . . . We both love Boston, all parts of it, and I think that's evident in the movie."

Affleck, who traveled to the Venice and Deauville film festivals in late summer with The Assassination of Jesse James team, doesn't expect to be starting anything new until next year. Married to Summer Phoenix - which makes his buddy Joaquin Phoenix his brother-in-law - Affleck has scripted a children's film, in development at Warner Bros. The couple have a 3-year-old boy.

"It's an animated feature about all the animals who were not chosen to go on Noah's Ark," he explains. "The ones left behind. It's called Aardvark Art's Ark. . . .

"It's not like making a regular movie," he adds. "You write it, and then you work with illustrators, and then they start to sketch characters, and then at some point it goes on to become animated, and I don't even know what those stages are. I'm sure there's rough animation, and then they bring in voices, and then they hone it and go back and forth and it takes like five years!"

Read Steven Rea's blog, "On Movies Online," at http://go.philly.com/onmoviesEndText