Octave Verbrugge, a powerful Belgian building contractor, met Hugo Saint-Laurent, a brilliant French engineer, during a business trip and made friends with him. Now that his bureau of expertise is experiencing difficulties with one of their important projects he has the idea to hire his friend to help resolve the problem. Hugo agrees and stays as a guest at Octave's home in Ghent, where the promoter lives with his two unmarried sisters, Françoise, a beautiful but mysterious woman, and Aurélie, a very strict and withdrawn lady.

Katja van Kalmpthout tells the story of a young woman caught between family expectations and her desire for independence. The daughter of newly wealthy parents, Katja rejects their plan to marry her off to a suitable suitor, determined to defy their petty-bourgeois prejudices. On her birthday, a grand party brings influential guests and potential matches to the family home, but Katja slips away to explore the city. There, she meets Chris, a recent graduate struggling to find work, and a tender romance blossoms. To stay with him, she must confront her parents’ rigid values, making for a charming and spirited tale of love, rebellion, and self-discovery.