In Chapter Six of Harper Lee's To Kill a Mockingbird, the suspense is delivered gradually, hinting in Scout's commentary that something that may take place—based on Scout's intuition and the unusual behavior of Jem and Dill.
The evening starts casually enough, as Jem asks his father for permission to visit the fishpool. Scout becomes uneasy when Dill suggests that they go for a walk.
Dill stretched, yawned, and said altogether too casually, "I know what, let's go for a walk."
He sounded fishy to me. Nobody in Maycomb just went for a walk.
When Jem is closed-mouthed about the boys' plans, Jem tells Scout she can go home if she wants to: something is definitely up if Jem shoos his sister off.
However, the tension increases as the children make their way under the garden fence. The suspense arises as sounds are described which would give away their presence:
Don't get in a row of collards whatever you do, they'll wake the dead.
When the fence is noisy, Jem takes care of it:
We came to the gate that divided the garden from the bacy yard. Jem touched it. The gate squeaked.
Spit on it, whispered Dill...
"Sh-h. Spit on it Scout."
As the children move around the house, Dill peers into a window, but sees only curtains. They decide to move to another window. Jem's foot causes more noise:
When Jem put his foot on the bottom step, the step squeaked.
When the children start to run, the plants make a sound—the same collards Jem had cautioned the other two about:
He flung open the gate, danced Dill and me through, and shooed us between two rows of swishing collards.
Scout is almost paralyzed by the next sound:
...as I tripped the roar of a shotgun shattered the neighborhood.
In all these instances, when the suspense is most heightened, the reader finds him-/herself on the edge of the seat because of the sensory details used by Lee—specifically auditory sounds. As they get louder, they become more frightening. The sounds parallel the movement of the children—the more dangerous their circumstances, the more sounds there are that frighten them until they find themselves fleeing the scene as if they were moving targets—with the shotgun sound still ringing in their years.