In Chapter 15, after the dissolute Tom steals the knife belonging to Luigi, Wilson devices a scheme to catch the thief. First of all, a five hundred dollar reward for the knife is publicly advertised; then, privately he offers a bounty to the pawnbrokers for the capture of the thief. In this way, the thief will not be worried about entering a pawnshop in order to sell the knife while at the same time the motivated brokers would quickly apprehend the thief. Tom uses this plan as proof that if the knife were really stolen, someone would have captured him/her by now. Wilson promises to have the case solved in a month.
In Chapter 19, Tom kills Judge Driscoll, dropping the knife. Luigi is, therefore, arrested. However, Wilson believes that the mysterious girl he once saw in the Driscoll house is behind the crime. For, he cannot consider Tom, who has too much vested interest in the judge's staying alive since it is illogical that Tom turn his aggression toward his benefactor; besides, it is against his best interest to kill the judge, who has supported him all his life. With the judge dead, Tom would have to get himself put back in the judge's will from which he has been removed. (Wilson does not know that the judge has reinstated Tom).
However, in Chapter 20, it is Pudd'nHead's hobby that solves the case for him. For, after Tom visits him, having picked up a glass slide with Roxana's name upon it, Wilson notices that something about Tom's fingerprints are odd. But, because he is fatigued, he goes on to bed. The next morning, Wilson has a startling realization that it is Tom's fingerprints on the knife; not only that, but the fingerprints of Tom do not match his fingerprints taken when he was a baby.
This evidence, then, solves the case; in addition, Wilson exposes Tom as a slave baby, not a free white man. So, he is now property. Through some legal , Wilson maneuvering to get Tom pardoned by the governor; however, he himself is "sold down the river" in payment to the Judge's creditors.