While at the port one night, Marina Quiroga, an eligible single woman and sister to the city's police chief, unexpectedly surprises a man who is stabbing a woman. This will awaken within Marina her instinct as a detective, and with the help of her loyal butler Héctor, she will start to investigate the crime.

The killer has managed to evade the police and Arturo is forced to recognise that there is in fact a killer on the loose threatening the general public. Meanwhile, Marina and Héctor discover a new clue that leads them to the identity of two women who are in grave danger. Searching for them, they end up in the Women's Quarters, where they confront the killer in an epic final battle.