"We have a system that works here," says Laura Leviani (Monica Bellucci), with alarming conviction; to which Kathryn Bolkovac (Rachel Weisz) correctly questions, "Oh really? For who?" Leviani is the unhelpful bureaucrat at the Global Displacement Agency refusing to help a girl out since she doesn't have the correct paperwork. It's a cruel irony, since the girl was trafficked from god knows where, and her passport is held by the same men who have been holding her captive, forcing her to engage in sexual acts she never signed up for. Bolkovac is one of many American recruits working for a private military company, Democra, who witnesses shocking events in post-war Bosnia. While many turn a blind-eye, Bolkovac has been trained to do the right thing, and investigating such sick corruption is nothing but obvious to a Nebraska cop.

Her new mission is initially filled with hope and excitement, who was struggling to balance her career and family as a divorced mother of two without the privilege of custody. For a few months' work, she is guaranteed tax-free 100,000 dollars, an opportunity she cannot afford to turn down. Her job consists of overseeing the rebuild of the war-torn country, where the civilians still struggle with racial and gender inequalities. Meanwhile, girls from neighbouring countries are being transported into Bosnia under false assurance. They are promised jobs - but instead they are trapped in disgusting rooms full of used condoms, drug needles, some questionable-looking mattresses, metal chains, and some urine pots. Ruled by fear and guns wielded by owners who aren't afraid to use them to protect their profits, the girls have no choice but to obey. Many of these girls are under-age, but the clients aren't too bothered about that. All they focus on is sex, and somehow asserting their masculinity by abusing these helpless girls.

And what a range of clients these girls are visited by. As Bolkovac slowly starts uncovering the disturbing truth, she realises how naïve she had been all along. She initially pin-points one person, a fellow employee of Democra whose sleezy, care-free and dismissive attitude doesn't sit well with the lone crusader. But she has failed to see the full picture. It's the local police, the international police task force (IPTF), high-level diplomats, employees of the United Nations, a lot whom can get away with all sorts of crime since they enjoy the benefit of hiding behind diplomatic immunity. "Immunity, not impunity" reminds Madeleine Rees (Vanessa Redgrave), a human rights advocate, and one of the very few people willing to help Bolkovac do her job. Worse, these people are not just hiring these girls for their pleasure, but seem to have an active part in actually bringing the girls in from various countries and flat-out deceiving them. Many of them with ties to the United Nations, a global charitable organisation so powerful and dominant that no-one can ever get near.

Bolkovac is far from perfect, and the film is not afraid to show us that she is in way over her head trying to tackle the world's biggest, most respected organisation. The one thing she knows to do for sure is to distinguish right from wrong. Rape, is wrong. Human trafficking, is wrong. Kidnapping and entrapment, are wrong. Shame, because she is the only one thinking with her head here. So she is naturally frustrated when people of the law and human rights prevent her from doing the right thing. Weisz, in one of her strongest, most unforgettable performances, is masterful in balancing the many complex emotions of her character as she is put through many obstacles. Compassion and anger are what drive the heroine, the former for the abused girls, and the latter towards the high-power officials arrogant and corrupt enough to believe they have what it takes to slip away without facing the appropriate consequences. She is quiet yet intense, and there isn't a hint of over-acting here, despite the subject material.

Yes, this is a somewhat fictional film, inspired true events, but many of its facts are based on the controversies surrounding the American company DynCorp, whose unlawful and unethical practices came under fire in 2002. Bolkovac (a woman who really does exist) saw illegal practices, reported them as such, and got fired because of it. DynCorp is still one of the largest private military companies funded by the States, and its operations all over the world, particularly in the Middle East, brings them billions of dollars in profits. Is the plot manipulative? Hardly, this is what actually happened. And being such a character-driven drama that this is, "The Whistleblower" walks that fine line of addressing the important key issues with confidence and passion, all the while not succumbing to too much preachy, calculating, self-righteous tone. It has a gentle, well-balanced mix of drama and thriller, in which neither aspect is overplayed.

Whilst it is mostly Weisz at the centre of this gripping material, strong supporting actors also lend their hand in completing a well-rounded cast. Redgrave, with her iconic warm yet stern voice and demeanour provides excellent assistance, arousing sympathy from the audience with her ever-so convincing looks of compassion, and she brings with her a trusted friend, Peter Ward (David Strathairn), an internal affairs officer who turns out to be one of Bolkovac's very few allies. Two veteran, accomplished actors, both with noticeably smaller roles than Weisz's, shine nonetheless in what precious little screen time they have.

Sometimes, there is a little too much going on, with too many characters and plot strands for the director to handle. We watch Bolkovac carry out her investigation almost single-handedly, we closely follow the victims and their troubled lives, there's the politics to consider, and sometimes the purposefully dim lighting goes annoyingly too far - so much so that it can be difficult to distinguish between the vast number of similar looking villains and victims. But a little convolution never hurts a conspiracy thriller. What sets "The Whistleblower" apart from similar themed films is how personal and sensitive the film's narrative is. Bolkovac travels alone, mostly in the dark, risking her life in order to finish what she rightfully started. She is out in the open, and in the volatile region she finds herself in, anything can happen. By using her vulnerability, it reels you in, and is more than effective in setting up a cruel, menacing atmosphere of the real world. This may not rank with the year's best films, but is certainly one of the most important. It's a much-needed wake-up call for us all, reminding us of the world we live in.