In 1870s New York City, affluent lawyer Newland Archer is engaged to the young and innocent May Welland. However, his world is turned upside down with the arrival of May's cousin, the enchanting and unconventional Countess Ellen Olenska. Ellen has separated from her husband and returned to New York society, seeking refuge and independence. Despite society's disapproval and the scandal that follows her, Ellen captivates Newland with her free spirit and modern views. Newland finds himself increasingly drawn to Ellen's intellect and charm, leading to an emotional and moral conflict as he begins questioning the rigid social expectations of his time.

As Newland becomes more involved in Ellen's life, he struggles to reconcile his duty to his fiancée May with his growing affection for Ellen. The intense pressure from their families and social circles further complicates matters, as both Newland and Ellen grapple with their desires and the implications of their actions. Through a series of intimate encounters and societal obligations, Newland must decide whether to adhere to tradition or follow his heart, setting the stage for a poignant exploration of passion, honor, and societal constraints in Victorian-era New York.