Various inmates accused of rape, murder and terrorism are released before their sentences are full; hours later, one of them is murdered, and Detectives Mora and Nieto take up case.

Isabel and Nieto investigate a new attack; terrorist Basauri is beaten up after being released; rapist Haro takes advantage of his freedom to spy on Isabel's life.

The investigation takes a hit after the monkey masks become a trend during Carnival; Haro's antics begin affecting Isabel's life, whose emotional stability is about to be put to the test.

Worried about Isabel's mental health, Nieto tries to get her out of the case to decrease her pressure; as the case gains attention in the media, the Ministry of the Interior calls for a tense meeting over the state of the investigation.

The murderer acts again, slaying a neo-Nazi; the former inmates rally in front of the station for protection, increasing the pressure on Isabel and Nieto.

The investigation takes Nieto to the zoo, where someone has freed all the monkeys from their cages; Haro continues playing with Isabel's psyche.