Hotel du Lac is the story of Edith Hope, a romance writer banished by her circle of friends to the title location, a hotel on Lake Geneva. Edith has left her life in a shambles after a disastrous affair. At the hotel she carefully considers her future and her conception of herself, determined not to let peer pressure drive her to change. She flirts with the idea of a relationship with the handsome Mr. Neville, another guest, but ultimately rejects it and strikes out on her own.
Edith reaches Hotel du Lac in a state of bewildered confusion at the turn of events in her life. After a secret and often lonely affair with a married man and an aborted marriage, she is banished by her friends. They advise her to go on "probation" so as to "grow up", "be a woman", and atone for her mistakes.
Edith comes to the hotel swearing not to change. However, the hotel's silent charms and her observations of the guests there all tug at Edith with questions about her identity, forcing her to examine who she is and what she has been. At the hotel, she observes people from different walks of life— Mrs Pusey and her daughter Jennifer, their love for each other, and the splendid oblivious lives they live; Mme de Bonneuil, who lives at the hotel in solitary expulsion from her son; and Monica, who came to the hotel acceding to her husband's demands. Edith falls for the ambiguous smile of Mr Neville, who asks for her hand in marriage.
She considers a life of recognition that being married to Neville would confer upon her, but ultimately rejects the possibility of a relationship with him when she realises he is an incorrigible womaniser. This also finally leads her to realise what her life is expected to be. Once again, she breaks chains and decides to take things into her own hands and leaves Hotel du Lac.