Alex Lewis is a contract killer living in Mexico who suffers from early onset Alzheimer's and works for Davana Sealman. He is assigned to kill a man in El Paso, Texas, where he grew up and where his brother lives in residence at a nursing home due to severe Alzheimer's disease. The target of the hit is Ellis Van Camp, a builder for the Texas Central Processing Facility. Meanwhile, Vincent Serra of the FBI's Child Exploitation Task Force is undercover in El Paso trying to arrest "Papa Leon," a sex trafficker who trafficked his thirteen-year-old daughter, Beatriz. Vincent kills Papa Leon after the latter takes Beatriz hostage during the sting. Beatriz is taken to the Processing Facility, where she had been held previously, before ending up at a group home. Vincent is frustrated that his domestic investigations into trafficking are frequently foiled, pointing to nefarious influences.

Alex kills Ellis and steals a flash drive from his safe. He finds out his second target is Beatriz, but after breaking into the group home, refuses to kill her as he believes children are "off limits." He threatens William Borden, Davana's lawyer, asking him to cancel the contract on Beatriz. Instead, she is killed by another hitman, Mauricio. The next morning Alex wakes in a hotel room after a one-night stand and sees news of Beatriz's murder. He realizes he is in danger and tells the woman he is with to stay in the room before heading for the parking garage. He and Mauricio get into a shootout, during which the woman is killed as she had followed Alex to deliver him his Alzheimer pills. Alex kills Mauricio and burns both bodies inside Mauricio's car.

Alex retreats to a former bakery once owned by his late father where he reviews the stolen flash drive and finds footage of Davana's son, Randy, sexually assaulting Beatriz. To avenge Beatriz, he kills Borden, which causes Randy to panic after realizing that whomever killed Van Camp and Borden will likely come for him. Davana tells her son to escape but he instead throws a party on his yacht. Vincent and his team, Mexican police detective Hugo Marquez, and Special Agent Linda Amistead, are investigating the Van Camp murder and realize that the recent crimes are connected because Van Camp and Borden were shot with bullets from the same silenced pistol. They find out that Randy is the owner of the Processing facility, Van Camp was the builder, and Borden was Randy's lawyer. The three realize that those connected to the facility end up dead and that Randy is likely next.

The FBI arrive at the yacht party to save Randy but Alex kills him first. Outside, he is cornered by Vincent and Marquez but escapes despite Marquez shooting him. Alex recovers inside the bakery but his Alzheimer symptoms are worsening, and he narrowly avoids an FBI raid, making his way to Davana's penthouse which is heavily guarded by corrupt El Paso police. He shoots his way past several police officers and reaches Davana but forgets that he had removed the firing pin from his pistol and is knocked out by Danny Mora, an El Paso police detective working for Davana. Mora brings him in alive to interrogate him about the flash drive but another officer tells Mora that Alex needs to be taken to the hospital.

Vincent, Hugo, and Linda receive a package mailed by Alex containing the flash drive.