What is the most significant episode/event in "All Summer in a Day"?
The most significant episode in the story is when the children lock Margot, the only child in the class who remembers the sun and the one most pining for sunshine, into a windowless closet right before the sun comes out on Venus for the one hour it will in seven years. Bradbury describes the closet as like a dark tunnel, shows us the door trembling as Margot bangs on it and throws herself against it, crying, and then the children "smiling" in the triumph of their cruelty as they head out into the emerging sun. Bradbury only needs to use that single word, smiling, to convey the children's sinister delight at thwarting Margot's deepest desire.
Bradbury then juxtaposes the horror of Margot in the dark closet against the joy of the children experiencing the sun. They forget her in their delight. Bradbury is a master of description and we see and feel with the children the flaming bronze sun, the sky like a giant blue tile, and the heat of the sun like an iron on their skin. However, as readers, Margot lurks in the back of our minds as we wonder if the children will remember her in time.