The novel is significantly concerned with the institution of marriage and the positives and negatives of matrimony. As part of its thematic exploration of marriage, the novel employs a “marriage plot.” Arising from late-18th and 19th-century sensation stories, the “marriage plot” is used, in academic literary discourse, to refer to the frequent recurrence of narratives in which marriage is the central concern and ultimate goal of a protagonist who is typically a woman. The marriage plot is commonly associated with authors such as Jane Austen and Charlotte Brontë, but its prevalence extends across continents and centuries; the marriage plot appears in English, American, and Canadian literature, from the 18th century into the present, for example. Under the demands of the marriage plot, women are dedicated to upholding the social project of heteronormativity and domesticity by framing the acquisition of a husband as the defining accomplishment of a woman’s life. In The Mystery of Mrs. Christie, Marie Benedict complicates traditional notions of the marriage plot by illustrating both The Promise and Peril of Marriage.

In the early sections of “The Manuscript,” Agatha Miller presents herself as eager and excited about the possibility of courtship and marriage.