"I am 100% French...and I am 100% Argentinian," says the Buenos Aires-born writer-director Lucia Cedron. Her family story played an important part in her debut feature Lamb Of God, the opening film at this year's Rotterdam International Film Festival. Cedron is the daughter of film-maker and political activist Jorge 'The Tiger' Cedron. In 1976, during the Argentinian dictatorship, her family went into exile in France. Jorge Cedron died in shadowy circumstances in Paris in 1980.

In 2002, at the height of the economic crisis in Argentina, Cedron decided to leave her life as a scriptwriter and documentary producer in France to return to South America. It was in Argentina she made her first short fictional film, En Ausencia, which won a Silver Bear in Berlin.

When Cedron first had the idea for Lamb Of God, she approached Argentina's best-known producer Lita Stantic (who has helped kick-start the careers of, among others, Pablo Trapero, Lucrecia Martel, Adrian Caetano and Diego Lerman). The formidable Stantic, notoriously selective about which projects she supports, decided to take Cedron on. Some 33 drafts of the screenplay later, Cedron was ready to shoot.

Lamb Of God is fictional but draws heavily on Cedron's background. The film is set both in 2002, during the economic breakdown, and in 1978. The events in each era echo one another. In 2002, a 77-year-old vet has just been kidnapped and held to ransom. His 30-year-old granddaughter desperately tries to raise the money to free him. As she does, she discovers more and more about the circumstances leading to the death of her father, a journalist and political activist, in 1978.

Cedron's earlier versions of the screenplay had received both a Coral award at the Havana film festival and a Sundance/NHK award. Nonetheless, she remained dissatisfied with what she had written.

"The script was very precise, like a Swiss clock, but it had no feeling and no point of view," she recalls. She therefore decided to rework the screenplay one more time and to give it "more heart". In doing so, she made it yet more complex. She is unapologetic about the elaborate flashback structure of Lamb Of God and the frequent flitting back and forth in time. "For me, this film is a love story. It is about three generations coming together. If they cannot forgive each other, at least they can try to understand each other."

Stantic initially asked the young director to make the screenplay clearer. Cedron refused. "We fought a lot. That was part of the dynamic," the director says. She adds that signalling the flashbacks overtly would have been "an offence to my intelligence as a spectator. I like to be pushed."

Lamb Of God was put together as an Argentinian-French-Chilean co-production. The French co-producer was Serge Lalou of Les Films D'Ici. The film will be released in Argentina in April and in France in June, through Ad Vitam. Meanwhile, various other festival outings are in the offing. Lita Stantic Producciones is handling international sales.

Lucia cedron's cultural life

Favourite films: I love Tarkovsky and Kieslowski's Decalogue. One of my favourite films ever is La Jetee by Chris Marker.

Favourite recent book: Octavio Paz's In Light Of India.

Favourite newspaper: The satirical French weekly Le Canard Enchaine. It has the best and most independent journalists.

Favourite magazine: Cahiers Du Cinema isn't my favourite but I can't stop reading it.