Miss Beadle is writing homework assignments on the board one afternoon in school when some of the older boys, who are back in school after harvest, begin causing trouble. One drops a book for the third time, and a frustrated Miss Beadle tells him to leave it there because "it can't fall any farther." The boy's seatmate then drops a book, and then Willie Olson joins in the mayhem by hurling a chalkboard eraser at Laura's head. Laura in turn chucks the eraser back at Willie, and the two older boys behind him get into a shoving match, just as Harriet and Lars Hanson walk into the chaotic classroom. Miss Beadle dismisses class for the day, and Lars informs Miss Beadle that they'll be reviewing her position, unfortunately. Miss Beadle asks simply that she be told the outcome of their decision promptly. Harriet and Lars leave, Harriet clucking on the way out.
After the meeting is called by the school board to discuss the issue of Miss Beadle's inability to keep control over the oom, Charles is sent to give Miss Beadle the bad news: the board opted to give her job to someone whom they felt would keep better control. Charles adds that the decision was not unanimous. Miss Beadle tries to maintain a brave front, and tells Charles that she plans to get away for a little while. She then asks him not to tell the children, at least until a new teacher is found, because she doesn't want them to know just yet.
A few days later, Laura, Mary, and the other students meet their new teacher: Mr. Hannibal Applewood. He introduces himself and comes off as severe as his name. He spells out the oom rules one by one, indicating that even an erasure mark on a paper will result in a failing grade. The students stare at him in a mixture of awe and fear, except for one of the older boys, who passes a note to Laura. When Mr. Applewod glimpses the note underneath her left hand, Laura is forced to come forward with it. The note is mocking him, and Laura is forced to take punishment – a beating on the hand with his stick – for the contents of the note.
That evening, Charles and Caroline are dismayed at the bad start at which Laura has had, and attribute it to Laura not generally doing as well in school as Mary. Over at the Oleson's, Harriet has the new teacher over for dinner and does further damage to Laura's image in Mr. Applewood's eyes when she decries Laura as a former "teacher's pet."
Things continue to go badly for Laura, even though she works hard to redeem herself in Applewood's eyes. Staying in from recess to work on her homework, Laura is the prime suspect when Applewood returns from lunch to find that ink has been spilled all over his bag. As the children laugh hysterically, Mr. Applewood assumes the perpetrator was Laura, calls her to his desk, and expels her from school, right on the spot. A tearful Laura runs home to find Pa, and sobbing, explains what happened.
Charles returns to the school the next day to confront Mr. Applewood and claims that while his daughter isn't perfect, she usually tells the truth. Grudgingly, Mr. Applewood accepts Charles' suggestion that with a back door to the school, someone else might have slipped in and spilled the ink in his bag. He reluctantly agrees to let Laura return, and even lets her ring the bell. However, Laura's relief is short-lived when her gaze locks with his, and she realizes he still suspects her.
Miss Beadle returns after her time away and runs into Laura, who explains how much they've missed her. Miss Beadle reminds her to keep working diligently and not to let anything stand in the way of that. Meanwhile, back in the school, chaos ensues as Mr. Applewood can't control the older boys. When he orders one of them to the front of the to have his palm beaten with a stick, the boy simply laughs in his face as the teacher hits his hand with all his might. Red-faced, Mr. Applewood realizes in a rage that he is powerless to do any more than Miss Beadle was able.
One morning, Charles happens to walk into the school with Laura's homework just as Mr. Applewood is about yet again to unleash his wrath onto the girl. Mr. Applewood is flustered when he realizes Charles witnessed his outburst, and Charles tells Mary and Laura to go home immediately. He then takes Hannibal's pointer stick – the source of numerous unjust punishments – and breaks it in half over his knee before stomping off.
The school board is assembled yet again to discuss their latest problem – an out-of-control teacher with a problem temper. Even while they are questioning Applewood, the man begins to get upset. He explains how he was sent to Walnut Grove on a mission to maintain order, and that he must be allowed to do his job. The entire school board watches on in awe and disbelief as the man begins to lose it – losing his cool in a crescendo of rage and shakes. When he realizes how he's unraveled in front of them, Mr. Applewood announces that he will have his things packed and ready to go in the morning.
Miss Beadle is once again restored as teacher to Walnut Grove, much to everyone's joy. On her first day back, one of the older boys drops a book again. The entire class – including even the normally disruptive Willie – turn to look at him with evil eyes. Feeling their scorn, the boy apologizes to Miss Beadle, saying "It won't happen again, Ma'am." Miss Beadle returns to the chalkboard with a secret smile on her face, knowing that her students have come to her rescue.