The book follows Linda, a woman who seemingly has everything—a loving family, a successful career, and financial security—yet feels a profound sense of listlessness and "emptiness". The narrative develops around her choice to risk her stable life by starting an affair with a former boyfriend, which serves as a catalyst for her to confront the "abysses of her soul". Key Themes Developed in "Untreue":
: The story contrasts the safety of routine with the dangerous thrill of passion. Linda's journey is presented as a search for the "meaning of life" beyond societal expectations.
In Paulo Coelho's novel (English title: Adultery ), the "feature" or core element developed throughout the story is the reawakening of a dormant soul through a daring, albeit destructive, adventure.
: Coelho explores how a "perfect" life can lead to apathy, suggesting that humans sometimes need to feel more , even if that feeling comes from pain or risk.