Las Cumbres Boarding School is an impenetrable fortress built on the edge of a cliff where students are subjected to strict discipline and it seems impossible to escape. Two of them manage to run into the woods one night, but things take a turn for the worse because surviving outside the school is even more dangerous than inside and the woods are much more terrifying.

Amaia is lost in the woods when she’s found and taken back to the school where 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 she’s accused of tattling. Paul and Amaia take Paz and Eric to see a mysterious painting with crow-men, but they find something terrifying instead. Inés undergoes treatment and takes pills that give her hallucinations. Elías and Elvira feel an increasingly irresistible attraction and Paul and Amaia will discover something about Las Cumbres.

Amaia and Paul manage to find the Crow’s Nest. Meanwhile, Inés wakes up confused in the middle of the woods and when she sees León, she runs in terror. We go back in time to discover the secret behind Inés’ connection to León. Eric suffers another episode of memory loss. Elías notices some strange behaviors, which start to raise his suspicions.

One student dead, another student missing, and the kids get framed when the headmaster's search turns up ecstasy among their possessions.

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.