Pozdnyshev is very wealthy, a member of the Zemstvo (a level of rural government in Russia), and a very jealous husband. He believes that his wife is having an affair with the violinist Trukhachevsky, though he has seen no real evidence. He has been jealous of other men before, but Trukhachevsky is different because of his connection to Pozdnyshev's wife through music. Pozdnyshev believes that music leads to infidelity. After returning home to find Trukhachevsky and his wife having dinner together, Pozdnyshev grabs a dagger and creeps through the house to avoid detection. When he bursts into the dining room, they are doing nothing but eating, but he believes that his wife's face betrays her disappointment at his interruption of their romantic meal. He stabs her in the side, and she dies later that day. After spending 11 months in jail, Pozdnyshev is acquitted at trial because of his wife's perceived infidelity. Pozdnyshev has come to believe that true love does not exist and that it was inevitable that he would kill his wife. He expresses regret over her death in the end but says that the lesson to be learned is that he never should have married in the first place.
Pozdnyshev's wife's name is never given, despite her being a major character in the novella. This is because the story is told from the point of view of Pozdnyshev, and he does not view her as her own person; her role is to be his wife and the mother of his five children. She is a talented pianist and begins to play music again when she has finished nursing her children. She forms a friendship with Trukhachevsky, a fellow musician. They play music together and enjoy each other's company. Pozdnyshev believes them to be having an affair, but there is no real evidence of such, and she denies it. Nevertheless, upon returning home to find his wife and Trukhachevsky having dinner together, Pozdnyshev attacks his wife with a curved dagger, dealing her a fatal wound.
Trukhachevsky is an unmarried man with a "pretty face" and an "external elegance." He dresses well and has a fashionable hairstyle and a waxed moustache. A talented violinist, he enjoys playing music with Pozdnyshev's wife, and they perform Beethoven's Kreutzer Sonata together at a dinner party. Pozdnyshev thinks that Trukhachevsky is having an affair with his wife, but there is no real evidence to support his belief.