As a child in Bogota, Cataleya witnesses the cold-blooded murder of her parents by drug lord Don Luis (Beto Benites) and his lieutenant Marco (Jordi Mollà).
"Don Luis has 'super bad guy' written all over him, but he's not the real source of danger," says Megaton. "It's actually Marco who unleashes peril and adversity. He does Don Luis' dirty work."
Cataleya takes refuge in the United States under the care of her mob boss uncle, Emilio (Cliff Curtis). The emotional damage from the gruesome murders still haunts every inch of her soul. She harbours thoughts of revenge but conceals them from her uncle. One day she convinces Emilio to show her the way of the assassin. He agrees, but only under the condition that she remains in school.
Fifteen years later, she's a fully-fledged contract killer working for her uncle, and her thirst for revenge has not subsided. She feels a sense of urgency to seek the men responsible for her parents' deaths and to seek justice- even it means risking all that is dear to her.
Ever since the success of 1994's The Professional, Luc Besson (producer/screenwriter for Colombiana, and writer and director of The Professional) had expressed interest in working with Megaton on a sequel. That never happened, but they both clung to the idea of having a female hero in an action film.
"As for me, I'd been wanting to make a Jason Bourne-type action film with a female hero," says Megaton, referring to the hero of The Bourne Identity and its sequels. "I wanted to make a more serious, less cartoony film than Transporter 3. So Colombiana was ideal."
Preparing for the role of the spiritually-torn Cataleya was no easy task for Saldana, 33, who may be hard to recognise without her blue Navi skin. She played Neytiri in the highest-grossing movie of all time, Avatar. Megaton initially thought it was a gamble to cast Saldana, but he soon knew it was a logical choice.
For Saldana, it didn't take much to accept the role; she was instantly drawn to the complexity of Cataleya.
"She has a dual nature- she's simultaneously single-minded, athletic, cunning," says Saldana, "but she's also fragile, alone and exhausted by vengeance that's eating away at her, but that drives her as well. Because that's her goal, she owes it to herself to see it through."
Colombiana opens on Thursday. Contains scenes of violence and adult content