Plot

A slave switches her light-skinned baby with her master's baby. The child grows up raised by whites.

In the mid-19th century, lawyer Pudd'nhead Wilson suffers the mockery of the community because of his obsession with fingerprints. Two of his samples are the infant prints of Tom Driscoll, the son of a white woman, and Chambers, whose mother is a mulatto nurse. Both boys have the same father, however, and both are about the same age, and after their birth, Roxy, angry at the Driscolls, switches them. Then, the false Tom murders his uncle and tries to blame his valet for the crime. Pudd'nhead defends the accused, and while comparing new fingerprint samples against the old, discovers the switch that was made years before. He then convinces an initially doubting jury to accept the infallibility of fingerprint evidence, after which the real Tom is restored as the Driscoll heir and the false one goes to jail.—Pamela Short

Lawyer Wilson, a young man, comes to a small Missouri town to practice. On his first day in town, angered at a dog snapping at his heels, he remarks, "I wish I owned half of that dog. If I did, I would kill my half." The subtlety of this remark passed over the heads of the townspeople as they couldn't figure out what would become of the other half of the dog if Wilson killed his half. This remark, his eccentric speech and his habit of securing thumb-prints from everyone with whom he came in contact, induced one of the town wits to call him "Pudd'nhead." This nickname blighted his career as a lawyer, but he managed to eke out a fairly good existence. With his small glass slips, he secures, among others, the thumb-prints of Tim Driscoll, age six months, and at the same time, the prints of Chambers, the six and a half months old baby of Roxy, the mulatto slave owned by the Driscoll family. These babies have the same father and look much alike. Roxy, angered at the head of the Driscoll house, changes the babies and passes off her child as the heir to the Driscoll fortune and makes the rightful heir the son of the slave. Twenty years later the false Tom Driscoll returns from college, accompanied by Chambers, his negro valet, who in reality, is the real Tom. His father having left him bankrupt and being unable to obtain money from his uncle, Tom sells his real mother as a slave and later, when caught trying to rob the cash box, murders his uncle. Tom falls in love with the beautiful Rowena Cooper, who has come down from "up North" for a visit with the Driscolls. Pudd'nhead Wilson also takes an interest in the fair Yankee girl, but she becomes interested in the slave, Chambers. After murdering his uncle and jealous of Rowena's attention to Chambers, Tom tries to fix the crime on him and Chambers is about to be lynched by the indignant whites when Pudd'nhead announces that he is the slave's attorney and insists upon a trial. Until the night before the trial, Wilson is unable to find any clue as to the identity of the murderer. With but a few hours to spare, he suddenly discovers that there is a tangle in the fingerprint records of the two men. In the courtroom all evidence points toward Chambers' guilt. Suddenly, in spite of the laughter, Pudd'nhead advances his queer fingerprint theories and convinces the jury that they are undeniable. He forces Roxy to confess that she changed the children in their cradle and that Chambers is the real heir to the Driscoll fortune and white, while Tom is in reality the slave. While Chambers goes to tell Rowena of his love, Tom is led away to jail.—Moving Picture World synopsis