Nels catches Willie with his hand in the jelly bean jar. To discourage him from doing it again, he decides he should have no supper. Mrs. Oleson overhears this and tries to object, sparking the latest argument in the Oleson household.
Later, Mrs. Oleson burns the family's dinner. This, while Nels has to run to Nellie's restaurant to cook a large family supper. Willie once again tries to appeal his punishment.
Henpecked for the last time, Nels finally blows his top and declares he's leaving.
Well, not really, But he does start a mobile mercantile, one he can run without any interference from his wife. Mrs. Oleson tries to get her husband to reconsider, but Nels decides it's best to spend some time apart before somebody does something they'll later regret.
Meanwhile, Charles has forgotten his anniversary and is in the doghouse with Caroline. To make it up, he buys her some perfume. He also uses some of his patented sweet-talking to patch things up with Caroline. She tries to resist, but it works.
After a hard day's work in rural Minnesota, Nels stops at a boarding house in Tracy, where he meets the beautiful proprietor - Molly Reardon. She has a wonderful accent, a great disposition ...and best of all, she can cook. Nels and Molly really hit it off.
And I mean really hit it off. It's obvious there is chemistry between the two, chemistry that is seriously missing from Nels' own marriage to Mrs. Oleson. Speaking of which, when Molly asks Nels if he is married, he says no and quickly excuses himself to go to bed. Later, he regrets lying to her, but he doesn't know what to do. br />
The mobile mercantile is a success, and Nels soon returns home to Walnut Grove, where Mrs. Oleson, Nellie and Willie immediately smother the family patriarch. Nels just wants to rest before getting a bigger stock to take with him on his next trip. Mrs. Oleson tries to talk to him and be intimate with him that night, but he is very standoffish. It is obvious that there is a distinct lack of love in the Olesons' marriage at this point.
On his next trip, Nels returns to the boarding house in Tracy, and once again assumes his new relationship with Molly. The two dance an Irish jig (to a relatively new medium called the phonograph). Later, Nels gives Molly a beautiful camiole as a gift for her generosity, and they kiss--rather passionately, too.
It's at this time that Charles - who happens to be on an overnight delivery run in the area - stops at the boarding house to look for a place to stay. He walks in and sees his friend kissing someone who is not his wife. Rather than make a big scene, Charles politely excuses himself and leaves quickly.
Nels later returns to Walnut Grove to explain the whole thing to Charles. Nels pleads with Charles to understand and to not tell Mrs. Oleson about what happened. Nels explains that Molly is a kind and wonderful woman, and that he loves his wife, but he's all mixed up, and he needs time to sort it all out. But Charles reminds Nels that it's not up to him to understand, and that if anyone needs to explain things, it's Nels and that it's Mrs. Oleson who needs to understand.
Back in Walnut Grove, Mrs. Oleson notices that an expensive camiole is missing from the store's stock and is unaccounted for. Nels claims not to know what happened to it. He says that he probably dropped it while he was on the road, and that "that just happens sometimes." He then says he plans to take out an even bigger stock on his next road trip, one he may not return from.
Returning to Tracy, Nels sees Molly dancing with another older man, and storms to his room in a huff. Molly goes upstairs to talk to him, and he is very relieved to learn that the man is actually her father. But after another night of dancing to Irish music, Nels finally realizes that Molly's father is only a few years older than he, and that makes him uncomfortable. When the father leaves, Molly starts talking about marriage, and Nels knows now that it's time to break their relationship before it flares into love. He then admits he's married and apologizes for lying to her. He tells her good-bye and he decides to return to Walnut Grove first thing in the morning.
For once, Nels is happy to see his family. Mrs. Oleson tries to surprise him with a roast, but she burns it. She admits she tried her best, and Nels tells her it's all right because she did the very best she could. He promises to be a better husband to her, and then invites her out for a walk on the town. Mrs. Oleson gladly accepts, and the two happily walk arm in arm in the fresh night air.
Nels never mentions that he nearly had an affair with another woman, and Mrs. Oleson never finds out.