Miss Watson is the sister of the Widow Douglas and owner of the slave Jim. She does not appear in The Adventures of Tom Sawyer but is introduced soon into Adventures of Huckleberry Finn. She is strict and religious, and gives such a different portrayal of Providence from the Widow that Huckleberry Finn judges there must be two Providences, and prefers the Widow's, entirely.
Miss Watson initially promised never to sell Jim, but he once overhears her discussing doing so, so Jim runs away. In the closing pages of the book, after Tom Sawyer and Huck Finn break Jim out of Mr. Phelps' captivity (only for Jim to be recaptured after assisting an injured Tom), Tom reveals that Jim was actually a free man after all, as Miss Watson had passed away two months prior and freed Jim in her will.