The Ingall's have their crop wiped out yet again, but this time Charles decides to give up and leave Minnesota.
I sometimes think this episode is overlooked, it doesn't have the drama of "His Father's Son" or the tragedy of "Remember Me". What it does have is a real commitment to the values that Landon wanted to establish for the series -- the worth of a united family. There are many memorable lines and conversations, including Laura saying that a family that "pulls together can do anything", and Charles' out-loud realization the he decided to sell the farm without ever asking his wife or children ( a nice nod to 70s era sensibilities, and at the same time, to a recipe that probably was pretty important to pioneer families). This episode also sets up the romance between Mary and John Jr., something that continues into the next season and ends abruptly the season after that (pretty nice acting given that Radames Pera and Melissa Sue Anderson didn't like each other). The use of the older couple, the Simms, is also effective as a reminder of the type of people who established the midwestern farms of the American frontier.
David Rose really does an excellent job with the musical scoring here, adapting his bouncy and rather 70s style "young kids in love" trumpet arrangement common to "For the Love of Johnny Johnson" and "To See the World" into a full orchestral string composition, making it much grander and more sentimental. His theme for Mary Ingalls is also embellished, and there are flourishes added onto the main musical score near the end of the episode.
Maybe my only quibble is with the impossible time line hinted at in this episode and common to many entries in the series. Its seems possible that the Simms did homestead the land that the Ingalls owned forty years earlier, but its a lot less plausible that they were married in the same church that exists in Walnut Grove at the time of the story.