The detectives investigate the murder of Nina Wilsher, an interior designer. She was shot and killed in her apartment, but her very valuable paintings weren't stolen. Lupo and Bernard question Dr. Lucas Evra, with whom she argued outside her building. Van Buren suspects the victim's interior design business was a front for money laundering, but the detectives find out she was actually selling drugs.

In fact, she was shot by two teenage boys: Rafa Alvarez and Sammy Molina. They were both groomed as assassins for the Vela drug cartel in Mexico. Rafa's mother is too afraid for her family to help with the investigation, and the Velas have hired ruthless defence attorney Marcus Woll to represent the boys. It turns out that the Velas had Nina killed because she was the subject of a ''narcocorrido'' (a popular song about real-life drug gangs) promoting a rival cartel.

Eddie Blanco, who works for the Vela Cartel, is identified as recruiting the boys. The Velas use Woll to represent Blanco too, so Cutter successfully requests a judge get Woll recused as Rafa's lawyer. Rafa will not co-operate or even speak to his parents so, with the help of a child psychologist, Rubirosa appeals to him. He testifies to a Grand Jury that the Vela Cartel groomed him out in Mexico, then returned him to the US where he was told to complete his initiation by killing Nina Wilsher.

The Vela Cartel releases a new ''narcocorrido'' threatening Rubirosa. She refuses to step down from the case so instead, she and Cutter are given security. Woll forces a delay in the trial and, before Rafa can return to testify the following day, Sammy is murdered in the juvenile facility where he was being detained. Rafa is now too afraid to go to court and Rubirosa cannot change his mind.

In a subplot, Van Buren is losing her appetite because of cancer treatment, and is encouraged to smoke marijuana to help with her symptoms. When the chief finds out, he shares a story of his own experience with cancer, and gives her advice on hiding her drug use.

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* LeftHanging: The outcome of the case is never explicitly stated although it follows that the charges against Blanco would be dropped.
* RippedFromTheHeadlines: From controversy about ''narcocorrido'' music and its potential connection to the grooming of children by cartels.
* ThroughHisStomach: Rubirosa appeals to Rafa by having his mother send over food (''birria'', a spicy meat stew) for him during a meeting with his lawyer.
* TroublingUnchildlikeBehaviour: Rafa is a 14-year-old boy groomed as a professional killer by a drug cartel.