I'll Turn My Heart to Stone (1968)

On her deathbed and burdened with an uncomfortable and urgent secret, a single mother-of-two confides her fears to the village's priest, entrusting him with a revelatory letter, and the fate of her helpless little children: Dimitris and Anna. As the years go by, a grown-up Dimitris arrives in Athens in high hopes of creating a better future for himself and his sister, and much to his surprise, he finds love and the ideal job as a singer. Nevertheless, even though that fortune seems to have smiled upon Dimitris and Anna, the siblings are far from happy. Will they ever discover the envelope's mystery?