The first thing you see FBI agent Kate Macer do is kill someone—she plugs a Mexican cartel thug without a second thought during a raid to rescue hostages in a suburban Arizona rancher. But as writer/director Denis Villeneuve’s Sicario soon makes clear, the lengths to which she’s willing to go to prosecute the war on drugs may not be far enough. The cartels kill indiscriminately, send gruesome messages scribed in corpses, co-opt police and governments, and operate by abject loyalty and terror. How can you fight an enemy who will do almost anything to beat you?

That’s how Kate (Emily Blunt) finds herself tagging along with smug shadow operative Matt (Josh Brolin) and his enigmatic sidekick, Alejandro (Benicio Del Toro) as they take the war across the border. When Kate asks Matt what his plan is, he says, with a smirk, “To dramatically overreact.” Things go according to plan.

Sicario sets an uneasy course. It’s part allegory for the dangers of meeting your enemy on his level—especially the dehumanizing sub-basement where the cartels operate. At the same time, it’s also part police procedural and part action film, and thus liable for the satisfactions and occasional thrills those aspects bring. With Kate as your proxy, you clench your way through a tense confrontation at a border crossing. You descend into the starlight-scoped darkness of an underground tunnel filled with smoke, gunfire, and bleeding bodies. Villeneuve, the increasingly interesting French-Canadian auteur behind Prisoners and Enemy, ramps up the dread with overhead God shots of the sere border landscape, courtesy cinematographer Roger Deakins, and blasts from Johan Johansson’s groaning score. But he also infuses the going-after-the-bad-guys set pieces with grim adrenaline. It doesn’t feel good to enjoy this film, as much as it would seem to lend itself to that at times.

Like The Silence of the Lambs before it, Sicario gains potency through its focus on Kate, a capable person trying to do her job in a setting where she’s an outsider at the chromosomal level. That remove, and taking machismo out of the protagonist’s emotional palette, allows the true horrors of the situation in which she finds herself to come through. But she remains a little bit of a blank (as do all the Mexicans in the film). Del Toro, with his weary charisma and his character’s mysterious background, threatens to steal the show—with Villeneuve’s blessing, as it turns out. Imperfect, but powerful nonetheless.