Suspense is created through the use of foreshadowing.
Suspense is the interest a reader has in a story. It is the feeling of wondering what is going to happen and wanting to keep reading to find out. One way Bradbury creates suspense in this story is through the use of foreshadowing, which is when an author drops hints early in the story that help the reader make predictions.
There seems to be something wrong from the beginning of the story. Lydia Hadley wants her husband George to come look at the nursery or show it to a psychologist. This is not a normal occurrence, so the reader should begin to feel more and more uneasy. When we learn about the expensive HappyLife home that does everything for them, and the expensive nursery, we are more and more interested to know what is going on.
Once in the room, it is clear that this is where the problem is.
"Let's get out of this sun," he said. "This is a little too real. But I don't see anything wrong."
The fact that the parents are concerned about the nursery, and say that it is too real, foreshadows the ending when the animals eat the parents. The children’s reactions to their parents’ concerns also shows that they might be homicidal.
Bradbury’s story is suspenseful because it keeps us guessing. We get hints from the very beginning that something is wrong, and these hints directly foreshadow (hint at) the murder of the parents by their violence-obsessed spoiled children. There's a dark warning here. If you overindulge people, they become dangerous.