Five years vanish in the rugged Pyrenees mountains of Huesca when two young girls disappear without a trace. Then, unexpectedly, one – Ana – reappears, shrouded in mystery. The case is reopened, drawing seasoned Central Operative Unit (UCO) agents Santiago Baín and Sara Campos from Madrid. Joining forces with local officer Víctor Gamero, they embark on a complex investigation, desperately seeking answers not only about Ana’s return but also the lingering question: what happened to the other missing girl, Lucía?