Emily Blunt stars as FBI agent and SWAT team member Kate Macer, whose services are enlisted in voluntarily helping out a mysterious group of black ops law-enforcement agents headed by drug war advisor Matt Graver (Brolin) and partner in crime-fighting in former Colombian prosecutor Alejandro (Del Toro), who are operating under the usual radar in their effort to deal with the extremely dangerous Mexican drug cartels that have begun to take firm root on the U.S./Mexican border, and have even spilled over activities into the Southwestern U.S. She's in way over her head in the tasks at hand as she travels to the 'lion's den' of Mexico's Ciudad Juarez, where the drug cartels have complete dominion. Macer, a firm believe in the law and her duty to uphold it, sees her new partners tactics as not only illegal, but potentially immoral, but her desire to see justice done after a calamitous mishap that saw several of her fellow agents killed in a suburban Arizona house raid gives her the resolve necessary to see the people responsible go down, specifically cartel kingpin Fausto Alarcon.