Written from a third-person omniscient perspective that shifts between the points of view of Paul, a farmer, and Ellen, his wife, "The Lamp at Noon" begins with Ellen inside the couple's house. Ellen lights a lamp just before noon because three days of high winds have kicked up so much dust that the sunlight can't penetrate the air to reach their window. While waiting for her husband to come in for lunch, she stands transfixed at the window and worries about her baby, who won't stop crying. She would like to hold and console her baby, but she leaves him in his crib, where a fine-cloth muslin tent protects him from breathing in the dust that infiltrates the house.
When Paul enters, the couple can barely talk to each other; they argued that morning and the day before. Soon Ellen reignites the argument and insists that they leave the farm to live in town. Paul refuses to leave and insists that, while there are dust storms now, the dry years will end. Ellen says the weather isn't to blame and accuses him and other farmers of greedily trying to reap a yearly wheat crop when they should have practiced more responsible soil management. Paul accuses her of thinking more of herself than the baby, saying she wants to return to the wealthier lifestyle in town that she gave up when she married him. They have a short stand off about who has the bigger hardships, and Paul feels ashamed. He tries to go outside but Ellen pleads with him to stay. She says she worries when left alone, and that she feels caged and imagines running away. But Paul dismisses her pleas and goes out to his horses.
The narrative point of view follows Paul out to the stable. In the calm and peaceful stable, he contemplates his vision of a brighter future. When he feels the ribs of a malnourished horse, he realizes that Ellen might have been right and that he can't even keep his animals fed. He grooms his animals but can't stop picturing Ellen's face, illuminated in the dark. He understands that she has no faith in the future he envisions. The wind moving past the stable sounds like a woman's cry and Paul suddenly panics. He rushes to the house.
After seeing that Ellen is walking back and forth with the baby in her arms, he relaxes. He goes to his tool shed and reconsiders his plans for the farm. Taking Ellen's advice to plant more fibrous crops and getting cattle, he will recover the land to fertility. He decides to wait until the dust storm has died down to tell Ellen about his plans.
The winds subside at five o'clock. Paul looks out the door of his shed and sees how barren his fields are. He realizes that he has been deluding himself and that Ellen was right; there is no future there. He feeds his animals, considering what he will tell Ellen. However, Ellen and the baby are gone when he returns to the house.
Frantic, Paul searches the house and runs through the fields. He asks neighbors for help to find her in the waning dust storm. After two hours, Paul finds her lying down in the sand and clutching the baby. The baby is cold, but Ellen does not appear to acknowledge that he is dead. Speechless, Paul carries his wife and child back toward the farm. The story ends with Ellen telling Paul that he was right: the storm did die down, and a red sky means there is fair weather ahead.
