Las Cumbres boarding school is an impregnable fortress, built on the edge of a cliff, where students are subjected to an iron discipline and from where it seems impossible to escape. Even so, two of them manage to escape one night and go into the forest, but everything goes wrong because survival outside the boarding school is even more dangerous than inside and it is a more terrifying forest.

Amaia is lost in the woods when she's found and taken back to the school. There, she becomes obsessed with convincing Paul and his friends of what she saw and reporting it. But students at the school are cut off from the outside world. In the library, they find drawings of men wearing bird-like masks that confirm Amaia's story, but something terrible shocks them all.

Adéle tells Alba's secrets, which surprise everyone. Darío takes his daughter Inés home, near the school, where she has very strange visions. An unexpected postcard from Manuel assuring that he's all right discredits Amaia's story about his disappearance. León sneaks into Darío and Inés' home, the students organize a secret party and Elías and Elvira grow closer.

Adéle blames Amaia for the party and they accuse her of being a snitch. Paul and Amaia take Paz and Eric to see a mysterious painting with raven men, but instead they find something terrifying. Inés is subjected to a treatment and takes some pills that cause hallucinations. Elías and Elvira feel an increasingly irresistible attraction and Paul and Amaia will make a discovery about Las Cumbres.

The prior of the peaks believes that the devil roams the monastery at ease. Amaia discovers that something supernatural unites her with Inés. Elías has a great feeling of guilt after his meeting with Elvira. Meanwhile, Paul finds something in his cell that makes him suspicious of the friar. Eric suffers a strange blackout and Paul and Amaia follow a clue to find the Raven's Nest.

Amaia and Paul manage to find the Raven's Nest. Meanwhile, Inés wakes up in a daze in the middle of the forest and when she sees León, she escapes in terror. We go back to the past to discover the secret of the relationship that unites Inés and León. Eric has an episode of memory loss again. Elías observes some of the boy's strange behavior, which begins to arouse his suspicion.

We go back in time to find out what happened to Manuel after a masked man took him away. His friends are convinced that someone has kidnapped him and they try to access the Raven's Nest, where they assume that his captors have him. Meanwhile, Elías believes he has discovered what is behind the symptoms of Eric and other students at the center and who the culprits are.

The friends mourn Manuel. The prior discovers Elías has broken his vow of chastity and sends him to another monastery. Meanwhile, Elvira tries to share everything she knows and Inés starts putting pieces about her past together. But a new and unexpected death enrages the students, who start a rebellion at the school. Everything is out of control and we're in for an unexpected ending.