Pudd'nhead Wilson is a novel by the classic novelist Mark Twain. In this novel, a slave switches her child with the child of her master in order to protect him from the darker side of slavery. The child grows to be spoiled and cruel, treating his own mother with disdain until he learns the truth of his birth. Frightened of being discovered, this young man commits the one crime that will reveal the truth to everyone he has ever known and cause him to be sold down river, just as his mother once feared. Pudd'nhead Wilson is a fascinating study in human nature that entertains as it encourages its readers to consider the bigger questions of society.

Dawson's Landing is a small town on the Mississippi River that has always been a quiet, simple place to live. David Wilson chooses to settle here and begin his law career, but it will be more than twenty years before he has the opportunity to practice law because a foolish statement causes him to gain the reputation of an unintelligent man, or a pudd'nhead. Instead of the law, Wilson pursues other interests, including the collection of fingerprints. Wilson collects fingerprints from everyone in town, including several babies in town.

Roxana is a slave who gave birth to a son the same day her master's wife gave birth to his only surviving son. When Percy Driscoll, Roxana's master, is widowed, Roxana becomes the sole caretaker of his young son, Thomas. Many people in town comment how alike the two babies look. Roxana is a light skinned black woman and her son is as blond and fair skinned as young Thomas. When the babies are seven months old, Roxana becomes frightened by the thought that the master might one day sell her son down river. At first Roxana considers killing her child as well as herself. However, Roxana realizes it would be much simpler to switch the babies.

Roxana's son grows up as Tom Driscoll, the spoiled son of one of the richest men in town while Driscoll's biological son grows up as Chambers, the child of a slave. When Tom's father dies, Tom goes to live with his uncle, Judge Driscoll, while Roxana is freed and goes to work on a steamboat as a chambermaid. When Roxana returns to Dawson's Landing many years later, she finds Tom just as spoiled and cruel as ever. Roxana tells Tom the truth about his birth and promises to tell Judge Driscoll if he does not pay her half his allowance every month. Tom agrees. However, Roxana is only one of Tom's troubles. Tom also has a gambling habit and is in debt. Tom cannot ask his uncle to pay the debt because the last time he did that, Judge Driscoll threatened to take Tom out of his will. Instead, Tom has begun to rob his friends and neighbors to pay the debt.

A sensation spreads throughout Dawson's Landing when two strangers, foreigners with a title, come to town. Everyone is so fascinated with these gentlemen that they do not notice Tom robbing them blind while they visit the strangers. Later, Tom learns that a knife he stole from these strangers is worth a great deal, but that all the pawn brokers have been notified in order to help catch the thief. Tom cannot sell the knife, but he needs money to pay off his debt. Roxana comes up with a plan to put off Tom's creditors, but this plan fails when Tom is robbed. Instead, Roxana suggests that Tom sell her as a slave to get the money to pay his debts and then buy her back in a year. Tom agrees, but sells her down river to a cruel mistress who has her beaten in the fields. Roxana runs away and comes to Tom, who has already made a deal to turn her over to her new master.

Roxana threatens to tell Judge Driscoll about Tom's birth if he does not go to him and get the money needed to buy her freedom. Tom agrees, but instead of asking Judge Driscoll for the money, he decides to steal it. In the middle of the theft, Judge Driscoll catches Tom. Tom kills Judge Driscoll rather than be exposed as a thief. The crime is blamed on one of the strangers because the stranger attempted to call the Judge out for a duel and was refused. Not only this, but the murder weapon was the stranger's knife. However, Wilson recognizes Tom's fingerprints on the murder weapon. When Wilson goes back to check all of Tom's fingerprints, he also discovers the baby switch.

In court, Wilson proves Tom's guilt. Tom confesses and is convicted of murder. However, Percy Driscoll's creditors claim that they should be allowed to sell Tom to pay off the debts left from Percy's estate. Tom is given a pardon and sold down river. At the same time, Chambers, who is the real Thomas Driscoll, inherits all of Judge Driscoll's money. However, Chambers cannot read or write, feels out of place among the whites, and misses his life among the blacks.