In the exposition of All Summer in a Day, the children live on Venus where it rains constantly. It has been raining for 7 years and no one except for Margot can remember what it was like when the sun came out.
The children are waiting patiently because it is about to stop raining. They will only have one hour to play outside before it starts raining again and everyone has to come back inside.
Margot feels alone and isolated from the rest of the students. She hates living on Venus and wants to move back to Earth. The other students don't believe her that she remembers what the sun was like. Margot is bullied by the other students which makes her feel even more isolated and apart.
Right before the sun comes out for the first time in 7 years, the other children decide it would be funny to lock Margot in the locker. The children get so distracted by the sun coming out that they forgot that they put Margot in the locker.
Margot is locked inside the closet the entire time that the students were outside. She yelled and she screamed, but no one heard her or let her out. Everyone go to go outside and play in the sunshine except for Margot.
It's not until after the rain starts again do the students remember what they did to Margot. In the closing sentences of the story, the students feel really horrible for what they did and they open the closet. We do not know how Margot reacts or wwhat she does because the story ends.