Smerdyakov is Fyodor Pavlovich's servant and cook, a twenty-four-year-old epileptic whom the town takes to be the old man's son by a holy fool, Lizaveta, and who ends up as the murderer of his master.
He was born in Fyodor's garden, the night his mother, Fedorenta, gave birth and died; he was raised by Grigory and Marfa, and his surname comes from her nickname. He grew up solitary and proud, hanged cats when he was little, rejected books because they are all lies, and at the master's table proved, through a sophism about a martyred soldier, that renouncing the faith under torture was not a sin. He says he hates all of Russia and that it would have been better if the French had conquered it.
The servant listens to Ivan, and reads in his words what Ivan does not want to see. He informs him of the knocking code, of the money and of the account of forty thousand for each son, and advises him to drop everything. When Ivan leaves, he takes the departure as consent. After the old man's death, he confesses the crime to him and returns the money, saying the lesson was Ivan's: if there is no infinite God, there is no virtue.
Shortly afterward he hangs himself. Smerdyakov is the character through whom the book tests Ivan's idea, and he is not a simple villain: he is the person least capable of examining it, and for that reason he takes it to the end.