Through the reminiscences of Kate Hamilton, an African American woman living in rural Furlong County, Virginia, The Grass Widow reveals the effects of deceit and adultery on the marriage of a young, impressionable girl.
It is August, 1988, and on her porch Kate, now a sensitive, attractive woman of fifty-eight, contemplates events during her forty-year marriage to her philandering husband, Elmore, who five years earlier had a stroke when he discovered a letter indicating that Kate had been unfaithful. Feeling that she is partly to blame for his stroke, she has dutifully cared for him until he is almost recovered. Now she awaits the yearly homecoming visit of her sisters Olivia and Lydia, who want to sell the family farm and persuade Kate and Elmore to live with them in Pennsylvania. But Kate laments the disappearance of the large farms around their own property, realizing that the sale of theirs will hasten the disappearance of the small African American community which centers around her church, Canaan Baptist.
Kate's strong attachment to Furlong is also tied to her friendship with Myrtle Bless, an old civil rights activist and family friend, as well as to her church, and her duty to her marriage vows. Her sisters, long aware of the life she has led as Elmore's wife, badger her to come live with them even if he refuses. By the end of their visit she faces a dilemma. Should she go with her sisters or stay in Furlong and continue her life with Elmore? Then after the sudden death of Myrtle Bless, a freakish accident occurs, one that leads Kate to make a surprising choice.