Opie completed a novel in 1801 titled "Father and Daughter". Characterized as showing genuine fancy and pathos, the novel is about misled virtue and family reconciliation. After it came out, Opie began to publish regularly. Her volume of "Poems", published in 1802, went through six editions. Encouraged by her husband to continue writing, she published "Adeline Mowbray" (1804), an exploration of women's education, marriage, and the abolition of slavery. This novel in particular is noted for engaging the history of Opie's former friend Mary Wollstonecraft, whose relationship with the American Gilbert Imlay outside of marriage caused some scandal, as did her later marriage to the philosopher William Godwin. Godwin had previously argued against marriage as an institution by which women were owned as property, but when Wollstonecraft became pregnant, they married despite his prior beliefs. In the novel, Adeline becomes involved with a philosopher early on, who takes a firm stand against marriage, only to be convinced to marry a West Indian landowner against her better judgement. The novel also engages abolitionist sentiment, in the story of a mixed-race woman and her family, whom Adeline saves from poverty at some expense to herself.