The heroine is Olivia, a woman born to a white plantation owner and his black slave. According to the terms of her father's will, she is sent to England to marry her white cousin, Augustus, which will thereby ensure her large inheritance. If they do not marry, he gets nothing and it all passes to his brother. On the boat on the way over, Olivia befriends Mrs Honeywood and her son. On arrival, Olivia meets with some kindness but also a lot of prejudice, particularly from the brother's wife, Mrs. Merton. Augustus marries her despite hints that his heart lies elsewhere. After being very happy for a few months, it turns out that Augustus was previously secretly married, but made to believe that his wife was dead. She and their child are still alive and they are reunited. This puts Olivia into the brother's hands so she retreats to the Welsh borders with her maid Dido. Honeywood finds them and declares his love, but Olivia insists on considering herself as a widow to her husband, and that no one can supplant him in her memory. Eventually Olivia returns happily to Jamaica with Dido with a view to 'ameliorating the situation, in instructing the minds -- in mending the morals of our poor blacks."

The black maid, Dido, has extensive speech and is generally very positively portrayed, even if she is a bit of a "black mammy" figure (although I'm not sure that such a stereotype exists so early?). There is no other non-standard speech, partly because there is no interest in the plot in conversing with the lower orders.