A Bible salesman shows up at the home of Hulga Hopewell and her mother. Manley Pointer, the salesman, is unable to complete a sale, but Hulga, fascinated with him, meets him at the gate the next day. When they go into the barn, he seduces her, exploiting her vulnerability.
Hulga and her mother are constantly at odds. Mrs. Hopewell sent her daughter to college hoping she would find a husband, but Hulga returned home with a Ph.D. and still single. Hulga also changed her name from Joy to Hulga, frustrating her mother further. The fact that Hulga is a devout atheist rankles her Southern Christian mother.
When Manley Pointer shows up, he wheedles his way into the living room, and then to the dinner table. His open staring at Hulga awakens some need within her, as she agrees to meet him the next day. In the loft, he strips her of everything -- her glasses (which symbolize her perception) and even her wooden leg, which comes across as even more of an offense than taking her sexually would have, because she seemed willing to do that. He pushes her down when she tries to get her leg back, and then he leaves with her perception and even her belief in "good country people" when he wanders off with her leg and her glasses.
On the way out, he mentions that he once took a glass eye in a similar way. The fact that Hulga's mother, at the end, still considers Pointer "simple" indicates that she has not yet had the sort of experience that Hulga has had that day.