Plot

An idealistic FBI agent is enlisted by a government task force to aid in the escalating war against drugs at the border area between the U.S. and Mexico.

Kate Macer leads a Phoenix based kidnap response unit for the FBI. Following Kate's team leading a raid on a known drug den in nearby Chandler, Kate is recruited to work on a special ops team led by Matt Graver of the CIA, he who is on special assignment for the Department of Defense. They recruited her because they wanted someone with tactical procedures knowledge. Outwardly, the team's mission, which works behind a Delta Force team as its primary gun power as required, is to decapitate a Mexican drug cartel by capturing or dismembering the workings of the main players, cartel head Manuel Díaz, his second in command Guillermo Díaz (Manuel's brother), and drug lord Fausto Alarcón. Kate agrees to the assignment as she feels the work of this team would be more effective in stopping the drug trade in the US than the piecemeal work of her current kidnap response unit. The third on the team is a mysterious Hispanic or Latino man Kate only knows as Alejandro, and who she does not fully trust as she can tell that he is suffering from a very traumatic past. When Kate and the team arrive in El Paso for their first mission, Kate learns that the team's workings are not all they appear on the surface - many of the proceedings which would not be considered above board or legal - despite the end goal being as she knows it to be. Still largely in the dark and only given information on a need to know basis, Kate decides to stick it out with the team if only to discover all that she is not told while still believing in the end goal. She may have changing or at least mixed emotions as she learns more and more about what is going on, including the specific reason why she was recruited.—Huggo

FBI field agent Kate Macer is approached to join a special anti-drugs task force that also involves the Department of Defense and the Department of Justice. She is given very little information about the methods or aims of the task force, except that it is going after senior members of a Mexican drug cartel. She soon realizes that their methods are quite unorthodox, even potentially illegal, and the aim may be even more unconventional.—grantss

When FBI makes a raid on a cartel house in Arizona, they discover several bodies and two local police officers are killed by a booby trap. The leader of the operation Kate Macer is summoned to a meeting in the Department of Justice and Kate is invited to join a special force commanded by CIA Matt Graver to fight the cartels. The idealistic Kate brings her partner Reggie Wayne and they team up with the force. They learn that the team has the intent to promote havoc in the Sonora Cartel to force one well-known kingpin to come to Mexico to meet the drug lord Fausto Alarcon and find his whereabouts. But soon Kate finds that the assignments led by Matt and Alejandro are absolutely illegal and she discovers why she was invited to join the team.—Claudio Carvalho, Rio de Janeiro, Brazil

An idealistic FBI agent (Emily Blunt) is assigned to work a dangerous stretch of the US-Mexico border by her superior officer (Josh Brolin). She's exposed to the brutality of the Mexican drug cartel, and becomes partners with a defector from the cartel (Benicio Del Toro) who possesses keen knowledge about the organization. As she gets deeper into the ruthlessness and corruption surrounding the FBI sting to find the organizations leaders, her moral and professional boundaries are pushed to their breaking point..

In Mexico, Sicario means hit-man.

In Chandler, Arizona, FBI Critical Incident Response Group Agents Kate Macer (Emily Blunt) and Reggie Wayne (Daniel Kaluuya) lead a raid on a suspected Mexican cartel safe-house, where they discover dozens of decaying corpses embedded inside the walls of the house. Outside a booby trap on a trapdoor in the outhouse explodes and kills two policemen. The house is owned by Manuel Diaz.

Following the raid, Kate's boss recommends her for a Department of Justice special joint task force, overseen by Matt Graver (Josh Brolin) and the secretive Alejandro Gillick (Benicio Del Toro) a Mexican ex-prosecutor turned CIA-trained assassin. Kate's partner Reggie is considered to be too novice and not chosen for the task force. Kate is divorced and has not kids.

The objective of the task force is to apprehend the Sonora Cartel lieutenant Manuel Diaz (Bernardo Saracino) currently operating and hiding in the United States. Assured that the task force will bring Diaz and those responsible for the safe-house incident to justice, Kate joins. Kate is told that the team will be heading to El Paso, where Diaz is suspected to be hiding. Kate is kept under suspense about the details of the mission as Matt, Alejandro and Kate take a private plane to the army base in El Paso, Texas.

The team, which includes Delta Force operators, Deputy US Marshals, and CIA personnel, assembles in El Paso and travels to Ciudad Juarez, Mexico, to extradite Diaz's brother, Guillermo (Edgar Arreola). Kate suspects that both Matt and Alejandro are from the CIA. Matt refuses to answer and says that Kate volunteered for the operation as she only cleaning messes in Phoenix and now she had a genuine chance to get at the men responsible for the mess.

Guillermo is apprehended in a smooth and swift operation at the court-house and taken to the US by road. The team knows that the most probable location for an ambush is at the border crossing area.

While crossing the El Paso-Juarez border the convoy gets stuck in a traffic jam. While waiting for the jam to clear, the team notices suspicious vehicles getting into position around the convoy. The team knows it is about to be ambushed by low-level cartel hit-men, and the Americans launch a preemptive attack to kill the hit-men. During the gunfight, Kate is forced to kill a Mexican Federal Police officer, and is left visibly disturbed by the violence. This deeply shocks the conscientious Kate who now knows that Matt is CIA. Back in the U.S., Alejandro tortures Guillermo and learns that the cartel uses a tunnel near Nogales, Sonora, to smuggle drugs.

Reggie continues to keep a tab on Kate and meets her when she returns to Phoenix. Reggie and Kate begin to question the task force's illegal and seemingly inexplicable methods. Kate threatens Matt to tell the truth, or she walks. Finally, Matt reveals that the objective is not to apprehend Diaz as originally suggested, but to disrupt his drug operations to such a degree that Diaz will be summoned back to Mexico by his boss, elusive Sonora Cartel drug lord Fausto Alarcon. By following Díaz, they will bring Alarcon to justice. Alejandro says that Alarcon is responsible for countless deaths in Mexico and finding him would be like discovering a vaccine.

To disrupt Diaz's cash flow, the team raids a bank used by his money launderers. Kate and Reggie want to use their findings from the raid to mount a legal case against Diaz but are ordered to let it go - much to their frustration.

While commiserating at a bar, Reggie introduces Kate to Ted (Jon Bernthal), a friend and Phoenix police officer. Kate and Ted go to her apartment, but as they become passionate, Kate realizes Ted is with the cartel. In the ensuing struggle, Ted begins strangling Kate, when Alejandro suddenly appears and subdues him. Alejandro and Matt reveal that they used her as bait, knowing the cartel would try to assassinate her after she was seen at the bank raid. Alejandro and Matt torture Ted into revealing the names of other officers working for Diaz.

They soon learn that Diaz is being recalled to Mexico, as they hoped. Kate questions the good news, pointing out that they have no jurisdiction in Mexico. Matt states that she and Reggie were simply being used, as working with U.S. law officers grants the C.I.A. legal permission to continue. Angered, Reggie advises that he and Kate leave the task force, but she insists on joining a task force raid on the tunnel to learn more about the operation's true nature. At the Mexican end of the tunnel, Kate sees Alejandro kidnapping one of Diaz's drug mules, a corrupt Mexican police officer named Silvio (Maximiliano Hernandez).

Kate attempts to arrest Alejandro for his illegal act, but he shoots into her bulletproof vest angrily telling her to never point a gun at him again, before driving away with Silvio at gunpoint. Realizing that Alejandro is operating illegally with the task force's support, and that there was never any intention of bringing Alarcon and Diaz to justice through legal channels, Kate confronts Matt.

Matt explains that they are attempting to return to a time when a single cartel, Medellín, ran the drug trade. This monopoly gave the U.S. more control. Alejandro, who worked for Medellín, was brought on to topple the Sonora Cartel by assassinating Alarcon, thus reducing cartel competition. Alejandro's own motive is revenge: Alarcon had ordered the murder of Alejandro's wife and daughter.

In Mexico, Alejandro forces Silvio to drive him to Diaz, kills Silvio, and forces Diaz to continue to Alarcon. Reaching Alarcon's estate, Alejandro kills Diaz, all the guards, and the entire Alarcon family. Alejandro appears in Kate's apartment and forces her at gunpoint to sign a waiver legitimizing the operation. As he leaves, she aims her pistol at him but cannot bring herself to pull the trigger.

In Nogales, Sonora, Silvio's widow watches her son's soccer game. The game is briefly interrupted by the sound of gunfire, before continuing.