TV series about a high school philosophy teacher, Merlí, who teaches in an original way, and about the students of his class, including his own son, and the relationship, friendship, love, and problems between the students of the class.

Santi, a young high-school student with a serious physical reaction to sunlight, is forced by his health to move with his single mother to a shadowy, isolated village in the mountains of Spain where the inhabitants begin to reveal themselves as strangely xenophobic. When terrible, violent events begin to occur, Santi becomes first a pariah at school and then strongly suspected by the police of hideous murders. Santi himself, however, wonders if he is not the next victim.