Barcelona, 1940. Under a dictatorship that has closed progressive schools and persecuted their teachers, a small group of teachers takes the risk of opening a clandestine school. Behind a façade of obedience to the regime, they offer the girls something forbidden: their mother tongue and a space of freedom and emotional normality in times of terror. But surveillance is constant, and the real danger arrives when they decide to hide a teacher who has fled from the south, whose husband has been executed and who is trying to cross the border before suffering the same fate. Protecting her could cost them everything they have built.