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.

Now that they know where the killer's next victim is, they must get to her before the killer does. But just as Marina is beginning to gain her trust, the masked killer appears. Marina manages to save Margó and promises to give her protection. But Marina will soon discover that no one is who they claim to be and she shouldn't trust the people around her.