Clint Eastwood directs Angelina Jolie in 1920s lost child drama

CANNES, France (Reuters) - Clint Eastwood directs Angelina Jolie in a gripping 1920s drama based on the true story of a woman whose search for her missing son forced her to confront the Los Angeles police and a serial child killer.

There was confusion on Tuesday over the name of the movie, one of 22 entries in the main competition at the Cannes film festival this year. It was originally titled "The Changeling" but production notes re-named it "The Exchange".

Based on archives from Los Angeles City Hall that were about to be destroyed until screenwriter J. Michael Straczynski rescued them after a tip off, the story is about working class mother Christine Collins whose nine-year-old son goes missing.

A police force in desperate need of positive publicity says they have found the boy, but when Collins insists the child is not hers she is subjected to a smear campaign and sent to a psychiatric ward for five days.

With the help of a charismatic pastor, played by John Malkovich, Collins goes in search of the truth, exposing corruption and incompetence in the police force along the way.

Separately, a serial child killer is caught, and the two storylines begin to emerge.

"This woman, through her tenacious attitude, brought down the whole police department and the whole political structure -- the mayor was not re-elected," Eastwood said after a press screening, where "The Exchange" was applauded loudly.

"It's a great study on human characteristics, this one mother fighting against the whole city," added the 77-year-old.

Jolie, a mother who is also pregnant with twins, said it was a difficult role to play. The actress, 32, started working with Eastwood shortly after making "A Mighty Heart" in which she portrayed the pregnant wife of slain reporter Daniel Pearl.

"Certainly so much of it is being a mother and imagining, if this was happening to me, my pain and my frustration," she said.

"I lost my mother a few months before the film and to me she (Collins) is very much like my mother. My mother was very passive in many ways and very, very sweet but when it came to her children she was a lion."

MYSTIC RIVER, DIRTY HARRY

Comparisons were drawn during the press conference between "The Exchange" and Eastwood's "Mystic River", which stars Sean Penn who is also president of the jury deciding the awards in Cannes this year.

Eastwood even saw parallels with his role as a tough cop in "Dirty Harry", released 37 years ago.

"It also showed a tenacious police officer who wanted to fight against political bureaucracy all for the defense of the victim," he said.

Asked why he did not have an acting role in his latest movie, Eastwood replied:

"I'm too young to play one of the boys. There was just no role for me and I'm gradually, as you've probably noticed, working my way around to spending more time behind the camera than in front. That's something that is an inevitability."

Early critical reaction suggests Eastwood could be a strong contender for the coveted Palme d'Or for best film in Cannes.

"If you are going to come to a film festival that has a competition, you might as well be in the competition," he said.

"Whether you win something or not is not the point of it. A lot of good films have won and a lot of not-so-good films have won. That's the same with any awards ...like the Academy Award ... and what happens happens."