Kate Macer (Emily Blunt) is a tactical officer for the FBI who, while on a raid, uncovers disturbing evidence of how deeply the Mexican drug cartel has entrenched itself in suburban Arizona. She is subsequently sequestered into an inter-agency task-force, along with "DoD advisors" Alejandro Gillick (Benicio del Toro) and Matt Graver (Josh Brolin), which is tasked with dislodging this incursion on American soil. But Macer, kept in the dark about the details of the operation, soon finds her values being tested as she delves more deeply into this world of drugs, murder and corruption.

The film brings a forest-and-trees treatment to its material, both visually and thematically. A lot of the drama unfolds in domestic locations – in homes and hotels – where scenes linger on shared meals, sleeping bodies and sparsely-furnished rooms. Close-ups rest on discarded items or lined, tired faces – Blunt has played hard-nosed characters in the past, but never wearing this little makeup – while, in outdoor scenes, Steadicam is employed to give a street-level feel to the action. This is contrasted with Roger Deakins's intermittent yet frequent use of wide-angle cinematography, in the form of both landscape and aerial shots, which fosters a beautiful and disquieting 'big picture' perspective.

This juxtaposition of grand vantage points with tight and close shots is reflected in the drama. In Sicario, morally ambiguous characters are constantly making reference to the overriding mission or the goal to save lives and make a real difference. But thanks to the strong performances offered by the cast, we are also invited into the lives of these characters so that we can fully register how their personal circumstances also have meaning and weight. This fosters a holistic sense of morality, in which director Denis Villeneuve regards aspects of both personal and social justice in regards to the War on Drugs.

The promise of the film, that can be heard in the trailer, is that, "In the end, you will understand." But it is in the end that the film abandons all sense of subtlety and seeks to educate the audience in the manner of a thought experiment. This isn’t self-evidently a problem: thought experiments, like great art, can force people to rethink their own values. Take the trolley problem, for example: You are standing on a platform watching as an out-of-control train descends on a pedestrian crossing. You’re holding a lever which, if pulled, will flip the tracks and cause the train to derail, killing the three people inside it. But if you don’t pull the lever, then the train will plough through the small crowd of four pedestrians standing on the rails.

The experiment invites you to consider whether it is worse to act and kill three people than not to act and allow four people to die. But the problem is that thought experiments are highly contrived – and only get more contrived as you add variables to the experiment, such as by replacing the train passengers with orphaned nuns and the pedestrians with people who chew loudly – and this inhibits their real-world applicability. We know from psychology, after all, that how people answer a dilemma like this depends on how the question is phrased to them. Likewise, in this actual scenario, we wouldn't know how many people are on the train or have the time to make a considered decision. And the thought experiment doesn’t allow that, in a panic, I might pull the lever early enough to derail the train, but not soon enough to stop it careering through the intersection anyway. (Thus killing everyone.)

In this respect I found the ending of Sicario to be not only unsatisfying but intellectually insulting. The film exploits the language of cinema in order to position itself as a god-like objective observer, but it only does so to show that Macer, and therefore the audience, must ultimately affirm any illegal or unethical tactics adopted in trying to win the War on Drugs – which it only accomplishes by stacking the deck in favour of that conclusion over all others. The ending of Zero Dark Thirty, by contrast, leaves open the question of whether the War on Terror, and going after bin Laden, was worth it. Sicario instead opts for the forced perspective, which undermines all the craft that is on display in the film just in order that it can say to the audience, "Admit it, you support the War on Drugs. Go on, just say it, we all know you do."

There are other ways in which Sicario disappoints. Unlike Zero Dark Thirty, it shows torture as being an effective means by which to obtain information, again finding itself outclassed by Kathryn Bigelow's film. It doesn't show the nature of Macer's relationship with her colleague Reggie Wayne (Daniel Kaluuya), or offer any reason why he's even in the film. And it employs a tired trope of sexualised violence against its lead to punctuate a scene in a manner that just seems gratuitous and unnecessary and, in its aftermath, a little bit awkward.

There were plenty of aspects of the film that did work for me, and I was particularly enthralled with the simmering, understated build-up to the main action set pieces. But, for me, Sicario is a masterful film that takes too many sour turns to be deserving of any high acclaim. It is, for me, the close-but-no-cigar film of the year.