After a séance performed with a group of friends, rather for fun than out of conviction, a 17-year-old girl named Laura begins to experience strange events that gradually convince her and her family that there is an evil entity haunting her with the ultimate goal of ending her life. Dark spirits, ghosts of putrid little girls, ominous voices, marks on her skin, and other paranormal phenomena begin to haunt her wherever she goes. Tormented by these experiences, Laura is caught up in a spiral that makes her unable to discern between what is real and what is madness. In this situation, the only relief for Laura seems to be Lola, the new high-school psychologist, a rational woman who wants to find out what is really happening to the young girl.

Disturbed by Laura’s increasingly sinister behavior, her mother, Carmen, a very religious woman, decides to turn to the local parish for help. Asunción, Laura’s religion teacher, has witnessed the young girl’s condition develop, and she assures her parents that they are dealing with a case of demonic possession. The only possible solution is to consult with Padre Olmedo, one of the 15 exorcists authorized by the Vatican to handle such cases of possession. Even though Laura’s father is deeply skeptical and fears that such a ritual could aggravate his daughter’s condition, the insistence of his wife, the teacher, and the priest eventually precipitates the exorcism. Only God can help Laura. Thus, they finally take the young girl to an ancient convent, where the exorcist promises that he will fight the devil until he is cast out of the girl’s body.

In the meantime, Lola decides to look into Laura’s past, and she finds out that the young girl had previously suffered from serious psychological problems that her family did not know how to deal with due to their strong religious beliefs. But when Lola learns that Laura is missing, it is already too late. At the convent, the priest is about to begin a series of 13 exorcisms that will save Laura from the devil… but sometimes the only possible escape for a possessed person is death.

This film is inspirated on the testimonies of the people involved in the last exorcism performed by the Catholic Church in Spain.