Director Denis Villeneuve gives the brutal violence of the intractable drug war the action-movie treatment.

Emily Blunt as Kate Macer in Sicario.

Photo courtesy Richard Foreman Jr./SMPSP/Lionsgate

Sicario opens on a power chord of fear, nausea, and dread that resonates throughout the whole movie. After an introductory screen defining the title—it’s drug-cartel slang for hit man—the seventh feature film from Québécois director Denis Villeneuve (Incendies, Prisoners, Enemy) drops the viewer straight into the noise and chaos of a tense FBI raid on a cartel-owned house near Phoenix. The electronic soundtrack (by Icelandic composer Jóhann Jóhannsson) delivers a series of jolting sonic booms as a young field agent, Kate Macer (Emily Blunt), leads her team to an unexpected and macabre discovery: hidden in the walls of the house are dozens of decomposing bodies.

The raid turns up more than enough evidence to arrest the house’s owner, Manuel Diaz (Bernardo P. Saracino). But Kate’s Bureau bosses instruct her not to track down Diaz just yet. Matt (Josh Brolin), a wisecracking operative whose precise title and mission remain undisclosed, wants to wait until Diaz gets called down to Juarez by the big boss (Julio Cedillo), so that the whole cartel can be dismantled from the inside. Kate, a by-the-book type, is uncomfortable with the idea of using one target as a lure to catch another, not to mention suspicious of Matt’s apparent disregard for the potentially high body count his plan entails. That discomfort will give way to disgust after Kate volunteers for a team of federal and state agents headed south of the border to find a tunnel that allegedly leads directly to the kingpin’s highly fortified lair. And if Matt’s role in the operation seems veiled in mystery, he’s a poster child for transparency next to Alejandro (Benicio del Toro), a Mexican ex-prosecutor now working as a kind of freelance vigilante.

The world of Sicario—deliberately opaque law-enforcement officials, vicious criminal bosses, suspenseful desert raids filmed as if through night-vision goggles—is one we’ve seen onscreen a lot lately, not only in movies and TV shows about the drug trade but in war stories about Iraq and Afghanistan. (Sicario brought to mind Zero Dark Thirty more than any other recent film.) But Villeneuve shows us that world with a stark urgency that makes the moral questions the movie poses feel vividly real. Sicario’s plot isn’t intricate or hard to follow—there are no clues to remember or puzzles to solve. Rather than a birds’-eye procedural about a complex international mission, it’s a close-up of that mission from the point of view of the participant who understands it the least.

Kate wants to know why she, a notoriously clean cop, has been conscripted for a job this dirty. Meanwhile Alejandro, who has his own motives for infiltrating the hideout, keeps doing things that erase the distinction between “good guys” and “bad guys”—terms both he and Matt throw around carelessly and with an alarming lack of introspection. Still, Alejandro remains curiously protective of Kate, who’s been quite open about her willingness to blow the whistle on their whole murky operation.

The shifting balance of power and knowledge among these three people—Kate, Alejandro, and Matt—is the dramatic core of Sicario, but the screenplay, by Taylor Sheridan (better known as Deputy Chief David Hale on TV’s Sons of Anarchy), skimps on the kind of rich character development that might have made their characters feel more human. Of the three, only Alejandro is given a trace of a backstory; I’m not asking for flashbacks with lap dissolves and harps, but where does Kate come from? Why did she divorce the ex-husband to whom she alludes in a single terse line? Does she ever, I don’t know, watch TV in one of her various barren hotel rooms, or give herself pep talks in the mirror while brushing her teeth?

I know this is the age of tightlipped heroines with stoic thousand-yard stares—presumably these are the “strong women” people are always talking about needing more of in movies—but I would like to put in a word for action heroes, male or female, who let us get to know them a little better (aided by scripts that strive to understand who they are). Because Emily Blunt is Emily Blunt, with a face that registers shifts of feeling so finely she could have been a great silent-movie actress, Kate remains a person whose story (and constantly imperiled physical safety) the audience cares about. But with no sense of what conditions or experiences have made her into the morally scrupulous person she is, the character stays flat: Kate stands for the idea of good-copness in general, rather than embodying a specific cop who’s good (and bad) in her own specific way. Though Brolin’s character, too, could have used more meat on his bones, the actor is both funny and enraging as the macho wiseass Matt, while del Toro—who can sometimes lay it on a little thick for my taste—gives a beautifully judged performance in a potentially melodramatic part.

With that unsettling electronic score and the elegant cinematography of legendary DP Roger Deakins (who has worked with Villeneuve before, on Prisoners), Sicario sweeps the viewer up in its jagged, menacing rhythm. Something violent is always either happening or definitely about to happen any moment, and when it comes it’s usually even worse than you expected. The Mexican underworld’s practice of mutilating and displaying its victims’ corpses, both as trophies and deterrents to would-be double-crossers, is frequently and graphically on display. The movie’s two-hour running time passed in a fevered rush, leaving me as exhausted and tense as the increasingly hollow-eyed Kate.

Whatever Sicario’s dramatic deficits, no one could accuse it of being an oversimplified clean-up-the-streets thriller, out to provide audiences with a quick fix of action-movie catharsis. This is the drug war as seen through a long lens, with the moral and political intractability of the problem laid out as clearly as the road from El Paso to Juarez in a stunning aerial shot of the U.S.–Mexico border. Seen from that high, the flat, dusty expanse of land where the two countries meet and divide looks exactly the same on both sides.