No longer a mama's boy, Willie announces his engagement and plans to marry his sweetheart. All this upsets his mother greatly, who makes several attempts to get her way.
Mr. Edwards and the residents of Walnut Grove make friends with an orangutan. But the friendship and the fun-loving primate's life may be short-lived when Nancy and Mrs. Olesen cause trouble.
Jason Carter starts working for an old lady. Jason becomes great friends of the lady. However, Jason's mom believes the lady is being too nice. Jason is forbidden to work for the old lady until Sarah finds out that the lady will soon die.
Laura writes a book for a book writing contest. Her book is chosen. She travels to Minneapolis to work out a deal with the publisher. However, when the publisher wants her to change some parts in her book, she withdraws from the contest and goes back home.
The Older Brothers is a gang that used to have a notorious reputation. First they hold up Mr. Edwards but end up losing the money. Then they try to get ransom money for Mr. Edwards but that doesn't go very well.
When Mrs. Carter's mother dies, Sarah Carter's father comes to town. He tries to get the Carters to come with home back to New York. He wants the Carters to have a better life. The Carters tell him that home sweet home is in Walnut Grove. After a while, Sarah's father begins to understand while the Carters feel this way.
Jenny looses a necklace in a pond and almost drowns trying to get it. After the incident, she has partial brain damage and has to retrain herself to talk and walk. Jenny's friend, a retired doctor, helps Jenny to force herself to get better. Thanks to him, Jenny makes a complete recovery.
The people of Walnut Grove are at first excited when the railroad wants to build through the town. This excitement doesn't last long. The railroad tells several people that they must leave their houses. The people make a stand at the Carter's place. This delay in building convinces the railroad to find a different route.
Nellie returns to Walnut Grove and discovers that Nancy is a lot worse than she ever was. When Nancy isn't the center of attention, she runs away. Nels and Nellie search until they find her. Just when they think Nancy has learned a valuable lesson, she proves that she really hasn't.
Mr. Edwards keeps Matthew at his place, but Nancy Oleson tells on him. A judge comes and rules that Matthew be placed in an institution. Then Mr. Edwards makes a statement that everyone is crazy sometime. He convinces the judge to allow the boy to stay with Mr. Edwards.
A traveling side-show comes to Walnut Grove. The main attraction is a wild boy. The wild boy escapes and becomes friends with the Wilders. The boy turns out to be Matthew Roger and the reason he acts wild is become he is given morphine.
Harriet finds a bearer bond from Walnut Grove. She uses this to try to get people to follow her suggestions. She tells the town council that if she doesn't get her way, she will cash in the bond which would force the town to pay Mrs. Oleson over $10,000.
The Ingalls are forced to sell their house to the Carters and leave Walnut Grove to find a more promising life. Mrs. Carter begins printing a newspaper for Walnut Grove. Etta Plum becomes the teacher in Walnut Grove when Laura decides she wants to spend more time with Rose. Almanzo's brother, Royal, comes to Walnut Grove with his daughter, Jenny.