Two half brothers look so similar as infants that no one can tell them apart. One, the legitimate son of a rich man, is destined for a life of comfort, while the other is condemned to be a slave because he is part black. The mother of the would-be slave is also the nurse of the other; to give her son the best life possible, she switches the babies. Soon the boy who is given every advantage becomes spoiled and cruel. He takes sadistic pleasure in tormenting his half brother. As they grow older, the townspeople no longer notice that the boys look similar, and they readily accept that each is born to his station.
A local lawyer, David Wilson, has had a similar experience. On his first day in the village, he made an odd remark about a dog, and the townspeople gave him the condescending name "Pudd'nhead." Although he was a young, intelligent lawyer, he is unable to live down this name, so he toils in obscurity for over twenty years. Finally, he is presented with a complex murder trial—a chance to prove himself to the townspeople and shake this unjust label.