Duke Preminger is a respected Austrian noble who serves as the head of the Preminger household and is the grandfather of the protagonist, Nadja. As the father of both Colette and Herman, he holds a significant position within aristocratic society and is deeply obsessed with preserving the pride, reputation, and continuation of his family's noble name. Social status is of paramount importance to him, which historically made him very upset when his daughter Colette chose to disobey his wishes in order to be with Raymond, a man he disapproved of largely because Raymond was merely a music teacher rather than a person of suitable rank.

In terms of personality, Duke Preminger comes across as a cold and rigid individual whose primary concerns revolve around the position and legacy of his house. His obsession with nobility and outward respectability often overshadows any displays of warm familial affection. This is particularly evident in his poor relationship with his son, Herman. The Duke holds such a low opinion of his own son that he does not wish for his title to pass down to Herman in the future. Instead, he sets his sights on his granddaughter, Nadja, as the preferred heir to the Preminger legacy.

His role in the story is primarily that of a distant orchestrator. Convinced that Nadja is the rightful heiress, he hires two private investigators, Rosso and Bianco, to locate her. The Duke is strategically responsible for setting the broader plot in motion, as he was the one who sent Colette's belongings to the orphanage. This deliberate action was designed to ensure that Nadja would travel to Vienna, allowing him to eventually arrange the circumstances under which he could meet her and assess whether she is truly fit to be the heir to the Preminger family. He is motivated by a strict sense of dynastic duty, believing that the survival and honor of his house depend entirely on placing the correct person in line for succession. While he rarely engages directly in the emotional turmoil of the younger characters, his decisions regarding inheritance and legacy create the framework for the journey and challenges that Nadja must face.