The Power of Sympathy was Brown's first novel. The characters' struggles illustrate the dangers of seduction and the pitfalls of giving in to one's passions, while advocating the moral education of women and the use of rational thinking as ways to prevent the consequences of such actions.

In the storyline, the opening letters between Thomas Harrington and Jack Worthy reveal that Thomas has fallen for Harriot Fawcet, despite the reservations of his father. Harriot resists Thomas's initial advances, as he intends to make her his mistress; readers also find that Jack encourages Thomas to abandon his licentious motives in favor of properly courting Harriot. However, when Thomas and Harriot become engaged, Eliza Holmes becomes alarmed and exposes a deep family secret to Thomas's sister Myra: Harriot is in fact Thomas and Myra’s illegitimate half-sister. Mr. Harrington's one-time affair with Maria Fawcet resulted in Harriot's birth, which had to be kept a secret to maintain the family’s honor. Thus, Eliza’s mother-in-law, the late Mrs. Holmes, took Maria, Thomas and Harriot into her home. After Maria’s death, Harriot was raised by a family friend, Mrs. Francis.

Upon receiving the news of this family secret, Harriot and Thomas are devastated, as their relationship is incestuous and thus forbidden. Harriot falls into a grief-stricken consumption (a condition now referred to as tuberculosis), from which she is unable to recover. Thomas spirals into a deep depression and commits suicide after learning of Harriot's death.

The Power of Sympathy was first published by Isaiah Thomas in Boston on January 21, 1789, and sold at the price of nine shillings. The novel did not sell well.

The novel was first published anonymously, but was popularly attributed to Boston poet Sarah Wentworth Apthorp Morton because of the resemblance between the plot and a scandal in her family; Brown was not correctly identified as the author until 1894.

According to Wikipedia