In the waning days of the Spanish Civil War, a young boy named Carlos is left at an orphanage in the remote desert since his father died in the fighting. The orphanage, run by the kind-hearted Dr. Casares and strict headmistress Carmen, houses other children who have lost their parents to the war. Carlos quickly notices that the orphanage harbors mysteries, including the unexplained presence of an unexploded bomb in the courtyard from a recent airstrike and whispers of a ghostly apparition, a boy named Santi who disappeared on the night the bomb fell.

Carlos's efforts to fit in with the other boys lead to the discovery of secrets and lies within the orphanage's walls. As clashes between republican loyalists and nationalist forces come nearer, personal conflicts arise from hidden gold reserves meant to support the antifascist cause. Tensions are further inflamed by the presence of Jacinto, the orphanage's aggressive caretaker who has his own ambitions and a complex history with the institution. Amidst impending danger from the war and strife within, Carlos becomes increasingly entwined in unraveling the mystery of Santi, whose tragic past holds a vital key to the orphanage's dark history.