Lawrence creates a distinctly foreboding mood in "The Rocking-Horse Winner." There is a general sense of impending doom throughout the story, mostly centered around the characters' collective fixation on money. This foreboding mood is especially evident towards the end of the story, as the narrative nears its climax:
The Derby was drawing near, and [Paul] grew more and more tense. He hardly heard what was spoken to him, he was very frail, and his eyes were really uncanny. His mother had sudden strange seizures of uneasiness about him.
Here, the narrative's use of the word "uncanny"—meaning strange, mysterious, and unsettling—creates a feeling of unease around the subject of the Derby and Paul's gambling. As tension within the text increases, building toward a climax, this sense of foreboding and unease only becomes more and more pronounced. What's more, to increase tension around the subject of money, the narrative also uses foreshadowing:
Two nights before the Derby, [Hester] was at a big party in town, when one of her rushes of anxiety about her boy, her first-born, gripped her heart till she could hardly speak.
Hester's anxiety about her son's welfare only increases as the Derby—a high-stakes gambling opportunity—grows closer. Her "seizures of uneasiness" indicate that something will go terribly wrong, ultimately foreshadowing Paul's death at the end of the story.
Finally, it is important to note the role of magical realism in generating the story's sinister and uneasy mood. Houses can only "talk" in a figurative sense, yet in "The Rocking-Horse Winner," the characters quite literally hear voices that encourage their feelings of greed. This unnatural force thus contributes to an overall tone of uneasiness, reinforcing Lawrence's stance that greed and materialism are destructive.