Smerdyakov is the character in The Brothers Karamazov who murders Fyodor Karamazov. Pavel Fyodorovich Smerdyakov is Fyodor's rumored illegitimate son and household servant, working mainly as a cook and lackey.
The murder is deliberately presented as a puzzle. Dmitri has a strong motive: he quarrels violently with Fyodor over money and Grushenka, threatens to kill him, and is seen with money after the crime. Dmitri is therefore arrested and ultimately convicted, even though he insists he is innocent of the murder itself.
Smerdyakov later tells Ivan that he faked an epileptic seizure, killed Fyodor, and stole the money to implicate Dmitri. He also claims Ivan's philosophical remarks—especially the idea that without God everything is permissible—helped justify the crime. Ivan tries to expose the truth, but Smerdyakov hangs himself before the case can be properly reopened. The novel's title character set includes three legitimate brothers, but Smerdyakov is the hidden fourth son whose actions drive the tragedy.