Chekov sets the mood by using imagery in the opening. He describes the day:
THE whole sky had been overcast with rain-clouds from early morning; it was a still day, not hot, but heavy, as it is in grey dull weather when the clouds have been hanging over the country for a long while, when one expects rain and it does not come.
and foreshadows the themes of the story. The heavy overcast is symbolic of the obsession that Ivan will describe having taken over his brother Nicholai. The expectation of rain lets the readers expect a sad story.
Chekov then gives voice to the story of Nicholai through Ivan, who is the real protagonist of the story. This personal point of view, like the imagery, helps to highlight and better express the theme.
Chekov leds to Nicholai's downfall slowly. First, he just becomes stingy. Then, he marries an old woman for money, showing his greed. Then, he slowly starves her, showing his obsession and lack of humanity. It doesn't end there, though. Readers at this point are disgusted by Nicholai, but Chekov (through Ivan) leads readers from here to pity by describing his downward spiral. He becomes fat and lazy, and takes on the roll of a "gentlemen", but doesn't understand how ridiculous a figure he is. He doesn't even understand that his own gooseberries taste bitter. But Ivan understands, and changes as a result:
"Lord forgive us sinners!" he said
He uses imagery to develop his theme