"A person who allows treason hates himself for it." These words appear in the head of the reader who decided to consider for himself the novel "Adult Woman" by the famous German writer Theodor Fontane. This work reproduces the complex affective conflicts of the heroine who chose the path of betrayal. Her feelings, oscillating between love and guilt, her inner heartache and moral doubts follow the reader until the last page, leaving behind deep reflections on her own moral principles. Fontane expertly uses the heroine's internal monologues, supplementing them with descriptions of nature and mystical images that help to feel the depth of her suffering. "Adult Woman" is not only a story about love and betrayal, but, above all, a subtle psychological drama that will leave a mark in the heart of every reader.