Bart finds his old teacher's diary and learns a surprising secret. Then, Lisa discovers an even bigger surprise.
The episode opens on the Flanders' yard sale, all of Springfield was there and Flanders starts to worry about people being negligent with his for-sale items. He then sells Bart old books, which he tries to stunt with until he finds his teacher's old diary Bart burned.
After reading it, Bart becomes motivated to be a better student after he reads her complimenting him. he helps other people at the school, and gets an A at the test.
After Lisa suspects cheating and sees Bart try to achieve more, she reads the diary and realizes Krabappel wasn't talking about him, but her cat. That caused Lisa to get anxious, thinking that if she revealed the truth to Bart, it will hurt his feelings.
Later on, Bart gains confidence and enters the spelling bee, but Lisa knew that he would lose, and she told the truth to Bart. After that he gets extremely sad, until Flanders tells him about the family wanting to move, except for Edna, who wanted to stay in Springfield to help Bart and other under-achieving kids.
The episode ends with Ned looking at Edna's diary, which says that he made her life a living dream come true.