Alexander grows up in a small house with his loving grandmother. In order to avoid his father’s fate, on his tenth birthday, he promises her that he will never fall in love. Every Sunday, Alexander visits his father, who has retreated to live in the Vienna subway system since the death of Alexander’s mother. As a young adult, Alexander wants to be closer to his father and decides to take a job in a lost-and-found office in the underground. It is here that he meets the beautiful and vivacious Caro (Verena Altenberger) in her cute subway hatter store. Although Alexander has successfully resisted love before, now his self-imposed oath becomes a difficult promise to keep.