The war on drugs seems to stand in for the war on terror in Denis Villeneuve's "Sicario," a thriller that crisscrosses the Mexican-American border and delves into slippery moral territory. Its title is a Latin American term for "assassin" or "hit man," though who it refers to won't be revealed until the chilling climax.

The film's heroine is Kate Macer, a nose-to-the-grindstone FBI agent played with a convincing combination of resilience and vulnerability by Emily Blunt. We meet her closing in on a big fish from a Mexican cartel, though she ends up literally surrounded by corpses. Whatever difference Kate is making, it's a drop in a very dark ocean.

advertisement | advertise on newsday

Kate is cherry-picked to join a task force -- made up of whom, no one will say -- led by Matt Graver (Josh Brolin). His cocky smile and flippant flip-flops spell trouble, but his partner Alejandro (Benicio Del Toro) is more worrisome still, a quiet Colombian who leaves Kate's many questions dangling in midair. She reluctantly joins them, only to find herself consorting with gnarly mercenaries and black-ops types whose missions seem legally questionable at best. "Nothing will make sense to your American ears," Alejandro tells her. "But in the end, you will understand."

Villeneuve covered this territory in his previous film, "Prisoners," starring Hugh Jackman as a father whose search for his daughter leads him to kidnapping and torture. Both films pose the classic moral question of whether the ends justify the means -- the same question that has dogged America as it attempts to stanch terrorism and end wars in the Middle East. In "Sicario," Roger Deakins' dark, spooky cinematography recalls Nietzsche's famous warning about staring into the abyss -- it also stares into you.

Villeneuve's brooding style can sometimes mute his action, but "Sicario" has its share of jolts, including a close-quarters shootout filmed in both green and black-and-white night vision -- an aesthetic allusion to the war footage we've grown accustomed to seeing. The film ends with a seemingly innocuous image, of Mexican children playing soccer, that brings its troubling story full circle.