Witnessing a mob-related murder, single mother Rosa is forced at gunpoint into clearing up the crime scene. Her spotless work gets her noticed by the criminal family responsible for the killing.

The body of the murdered boxing manager is found and detectives Sandro and Gutiérrez are called in to investigate. The evidence leads them to the boxing club, and to their first encounter with Rosa.

While Rosa's son's health rapidly deteriorates, Sandro and Gutiérrez locate another murder victim, finding a potentially incriminating weapon at the scene.

As Rosa performs an inexplicable task, the detectives find another dead body at the zoo. While all indications point to suicide, Detective Sandro is unconvinced the man has been framed for the previous murder.

As Rosa's special cleaning duties now involve her in the world of illegal drugs, Detective Sandro is suspended from the murder investigation.

As Felipe's condition deteriorates, Rosa devotes herself fully to her criminal activities in order to save money and take him to the US for a cure. In another part of town, her friend María attends a casting call and mysteriously disappears.