Faced with the imminent death of his father, the town postman, Oscar returns to Mexico for the first time and finds that he is now the only man among the handful of women who inhabit this small place where telephones and internet never reached. While trying to return to the United States, he takes charge of the mail and thus learns the stories and wishes of the inhabitants, including a child who asks about his father's letters. Oscar writes him the long-awaited letters and begins to bond with him and with Martha, his mother. When he can finally leave, he no longer wants to and will have to decide between going back or staying and rebuilding his life.

Detective Castro is called to investigate a string of mysterious deaths at the newly opened Caborca prison, home to the country’s most dangerous criminals. When Juan, a man claiming his innocence in the murder of his wife, arrives, a series of eerie and unexplained paranormal events begin to unfold, deepening the mystery and terror within the prison walls.