Every time George and Lydia visit the nursery and see the veldt scene playing, their deaths are foreshadowed. They find George's chewed wallet and Lydia's bloody scarf on the floor of the nursery. The lions even seemingly come running at them as if attacking them early in the story, foreshadowing their end and sending them screaming from the nursery:
And here were the lions now, fifteen feet away, so real, so feverishly and startlingly real that you could feel the prickling fur on your hand, and your mouth was stuffed with the dusty upholstery smell of their heated pelts . . . and the sound of the matted lion lungs exhaling on the silent noontide, and the smell of meat from the panting, dripping mouths.
The lions stood looking at George and Lydia Hadley with terrible green-yellow eyes. . . .The lions came running at them.
The whole look and feel of the veldt is ominous and makes the parents uneasy. It is hot, dry, and predatory.
Further, the children lie to their parents about the nursery. They even change the scenery on the view screens to encourage the parents into thinking they are not always watching the veldt. They behave coldly to the parents, foreshadowing the disregard and lack of feeling that will allow them to lock the parents in the nursery to be consumed by the lions.