"You realize you are alone. You and your mother. Her hand trembles.
"Her hand trembles.
"Your belief in your private world is shattered. You fell Mother tremble. Why? Is she, too, doubtful? But she is bigger, stronger, more intelligent than yourself, isn't she? Does she, too, feel that intangible menace, that groping out of darkness, that crouching malignancy down below [in the ravine]? Is there, then, no strength in growing up? No solace in being an adult? no sanctuary in life? no flesh citadel strong enough to withstand the scrabbling assault of midnights? Doubts flush you. Ice cream lives again in your throat, stomach, spine, and limbs; you are instantly cold as a wind out of December-gone.
"You realize that all men are like this. That each person is to himself one alone. One oneness, a unit in society, but always afraid. Like here, standing. If you should scream, if you should holler for help, would it matter?"
I love the way Bradbury, having expanded the child's consciousness beyond any thought or fear he has ever before conceived, reduces him down to a little kid again, subverting even ice cream into a metaphor for terror. And then binds him in helpless silence -- "if you should" implies "but you likely won't."