The episode opens with children playing outside of the school house. Mary remarks, “Ms. Sims is nowhere in sight!” She decides to assemble the class because Ms. Sims said to do that if she’s ever late. Nellie’s mother runs up just as the bell is ringing to report that there will be no school for at least two weeks because Ms. Sims’ mother has the Measles.

In the next scene we see Laura happen upon a boy fishing. He tells her that he’s new in town. He calls her brown eyes until he asks her name. The boy introduces himself as Seth. He walks Laura home and notices Mary outside. He’s intrigued and asks who she is. Laura introduces them and Seth asks Mary if she’d like to take a walk the next day. As Seth and Mary walk away Laura is left looking sort of disappointed.

At dinner Laura says that Mary stole the new boy from her. Mary says that he’s a bit old for Laura. Music starts to play and we see Mary make a face like she is in pain. Ma asks her if she’s alright and Mary says that her eyes are just a little tired. Pa says it’s about time she had her eyes examined.

The next day. We see Seth chasing Mary on a hill. He catches her and they fall.

Laura is walking home and sees Seth at work. He says he’s really glad to see her because she can let Mary know that he’ll be a little bit late later on. Laura is surprised they’re seeing each other again. “Don’t it get boring?”

Later at Mary’s eye examination. The doctor says there is a little eye strain but basically she’s fine. Pa enters to discuss. The doctor suggests that she wear her eye glasses more.

That night Seth comes over to the Ingalls house for dinner. While Mary is walking Seth home they discuss Laura being jealous. We see them kiss from Laura’s bedroom window and Laura exclaims to herself, “I hate you, Mary Ingalls!”

The next night Mary is reading at the kitchen table with her new glasses. Pa notices that her nose is buried in the book. Mary explains that the new prescription isn’t much better than the old one.

Mary returns to the eye doctor with Pa. The doctor asks her if she’s had any illnesses in the past. Mary tells him she had Scarlet fever a long time ago. He seems to be surprised.

The doctor asks to see Pa in private. The doctor brings up the Scarlet fever and asks how bad it was. The doctor explains that the fever damages the nerves. He says that the condition only worsens. He tells Pa that Mary is going blind. He says that only a miracle could cure it.

Pa denies it. Pa won’t accept it.

Later Ma and Pa discuss how Mary’s eyes are getting worse, but Pa doesn’t report what the doctor said. We hear glass break and one of the Ingalls girls yells, “Pa, fire!”

They run into the house and see a chair on fire. Pa removes it from the house and Ma covers the rest with a blanket. Mary apologizes. She tells them that she was reading and it seemed so dark. She says she was holding the lantern and she dropped it. Ma and Pa decide that Pa will tell Mary she is going blind tomorrow.

The next day. Pa joins Mary by the stream. Mary says that she noticed something has been bothering him. Pa brings up the Scarlet fever and Mary says, “It’ll get better though.” Pa tells her the doctor thinks it will get worse. Mary exclaims, “I’m going to be blind?!”

Mary walks away from Pa. Pa is left with his sadness. He looks up to see Laura standing by a tree. The music gets more intense. The camera zooms in on Laura’s concerned face and she runs away.

Nighttime. While preparing for supper, we hear Mary scream for Pa from upstairs. She screams that she can’t see. She screams for him to hold her. She screams that it is dark.

The next day Ma and Pa go to the doctor to discuss what to do. He recommends a school for the blind in Iowa. When Ma proposes the idea to Mary she resists. She doesn’t see the point. She says, “No matter where I go, all there is is darkness.”