The atmosphere, or emotional tone, of Ray Bradbury's story is created through through the use of sensory descriptive words and the dialogue of the characters. Lydia's initial conversation with her husband immediately conveys the ambience of anxiety and dread as she asks him to look at the nursery. When they enter the virtual reality room, George comments,
"Let's get out of this sun...This is a little too real. But I don't see anything wrong."
Still, when the sinister vultures fly over them, Lydia comments, "Filthy creatures." She also notes that the lions have just finished eating something. When George reassures her it was a zebra or giraffe, Lydia asks him, "Are you sure?" This doubt and anxiety of Lydia clearly prefigure what is to happen to them.
Lydia's alarm is increased with the sound of a scream that she asks her husband if he has heard. Then she yells, "Watch out!" as the lions charge them; they bolt from the room.
Outside, in the hall, with the door slammed, he was laughing and she was crying, and they both stood appalled at the other's reaction.
This passage creates equivocation. Is Lydia merely being too emotional--perhaps, even hysterical; or, is George merely rationalizing and being obtuse? At any rate, the reader is somewhat disarmed as to the verity of what is happening in the veldt created by the rosy-cheeked Wendy and Peter.
However, as the narrative progresses, Lydia's concern that the house is regulating their lives becomes more and more apparent. After discussing the conditions of the children with his wife, George ponders how
[R]emarkable how the nursery caught the telepathic emanation of the children's minds and created life to fill their every desire.
He considers whether the children are too young for thoughts of death, but then recalls how children so often wish it on someone else. "Perhaps Lydia was right" about the house controlling their lives too much. So, George speaks to Wendy and Peter, who deny the existence of "any Africa."
"I'm sure you're mistaken, Father."
After George sees that the nursery has been changed to Green Mansions, he notices an old wallet of his, and Lydia creates another alarm in the reader with her question, "How did your wallet get there?" Finally, George admits,
"I'm beginning to wonder....I've noticed they've been decidedly cool toward us since [you forbade them to take the rocket to New York]"
Lydia hears something else: "Those screams--they sound familiar."
This dialogue of the parents creates a suspense that reaches its climax when George tells his psychologist friend, "I don't want them [the children] going any deeper into this, that's all." So, he closes the nursery and Peter tells his father, "Oh, I hate you!...I wish you were dead!"
But, George weakens when his wife agrees to the children's request for "just another moment of the nursery." Here the dread that has been created by the descriptions and dialogue comes to its climax with Lydia's fateful words. Wendy and Peter call to their parents and lock them inside the veldt.