Sicario opens with a shot of the war taking place along the Mexican-American border. An FBI kidnapping task force has tracked down the location of several hostages being held outside of Phoenix, Ariz. The response team, led by agent Kate Macer (Emily Blunt), begins to search the property only to find that they have stumbled onto something much more horrendous than originally thought. An errant shotgun blast through a wall leads the team to discover that dozens of bodies wrapped in plastic have been stuffed behind sheetrock, all victims of the Mexican drug cartels headquartered just miles away.
The next day Macer is called into a meeting by her boss (Victor Garber), only to be introduced to a mysterious agent (Josh Brolin) heading up a special unit, one which promises to take the war back over the border and cut the head off of the snake. Partnered with Alejandro (Benicio del Toro), a quietly intense Mexican lawyer who slowly begins to introduce Macer to the tactics that will be deployed by their team, the young agent begins to question the outfit's true motives.
The events at the beginning of Sicario are the catalyst from which everything that follows in the film is built upon. Once Macer's agent is introduced to the barbaric nature in which the Mexican cartel's do business, her personal ethics begin to slide, and before she knows it finds herself in a shoot-out surrounded by civilians on the bridge linking El Paso, Texas and Juarez, Mexico, with Alejandro clueing her in on the fact that anyone in a police uniform is a potential assassin as well.
The morality throughout Sicario isn't so much black and white as much as every character involved in this border war of sorts is dark gray at their core. The casting of Brolin must be taken as a nod toward No Country for Old Men, a film that this movie borrows heavily from, if not for plot points, then in the sense of foreboding that sits like a residue upon each frame of its runtime. Alejandro is a slightly more pleasant Anton Chigurh, and Blunt is a younger, more pleasant-to-look-at Tommy Lee Jones-esque law officer trying to make sense of a world that is growing uglier by the day. Cinematographer Roger Deakins shot both films as well.
Director Denis Villeneuve has positioned Sicario as his follow-up, and sister film of sorts, to 2013's Prisoners. That film, starring Hugh Jackman as a deeply religious father attempting to find his kidnapped daughter, dealt with the question of how far a moral person will go to right a wrong and how far you can push gaining justice before you make yourself a villain as well. These are questions that the Canadian filmmaker is fascinated with, and his continued study of American morals is a welcome change of pace for modern cinema aimed toward adults.
Villeneuve also points his camera toward the United States' attitude toward world policing by filling his film with law officers from various agencies who show no qualms about crossing neighboring countries' borders in an attempt to carry out missions they believe only they can accomplish. The scene at the heart of the film features our main characters and a military squad entering a tunnel that runs below the desert in order to kill the cartel members busily running drugs back and forth inside. This scene, with shots of the group gearing up in body armor and walking into the desert night, evokes images of movies involving our ongoing war in the Middle East. In the end, Villeneuve is making the point that, to many U.S. officials, there isn't much difference between the conflict in Afghanistan and the Mexican-American border.