Set in Edwardian London, Night and Day contrasts the daily lives and romantic attachments of two acquaintances, Katharine Hilbery and Mary Datchet. The novel examines the relationships between love, marriage, happiness, and success. It deals with issues concerning women's suffrage, if love and marriage can coexist, and if marriage is necessary for happiness. Motifs throughout the book include the stars and sky, the River Thames, and walks.