The story follows a female protagonist Constantia Dudley and her relationship with the mysterious Ormond. The Dudley family lives in New York where they get victimized by a trusted employee who embezzles their money and leave them in huge debt. They are forced to move to Philadelphia where they endure the loss of their mother, a yellow fever epidemic, rigors of winter and the exactions of landlords. Constantia, the daughter of the family, manages to keep the family afloat by her efforts and determination. Her luck changes when she meets Ormond, a wealthy military projector and conscientious atheist, who falls in love with her. Ormond helps the Dudley family to rise from poverty and makes numerous efforts to win Constantia's heart. The Secret Witness thematically focuses on the ways in which individuals change in reaction to their social environments. The novel thoroughly explores the republicanism and republican values common to the early American nation.