 A young nun named Marta Odera (Eugenia Tobal), finds herself struggling for her life, after making the worst mistake. One day, when she is in church, she meets Marta Fernandez, a woman who seems helpless at first, but ends up being her worst nightmare. In this story, we see these two women developing a very intense "friendship", full of psychosis, jealousy and violence, which can only lead to one thing: death.