It's the first day of the new school year and Zack promptly finds himself caught in a lie when he tells a new girl at school he met over the summer that he's in 9th grade. After sharing his dilemma with Miss Bliss, she encourages him to tell the truth, only to have disastrous results.

Zack breaks his father's new camcorder and has to find a way to make $300 in order to replace it before Mr. Morris finds out about it. Zack then talks Mikey and the rest of the class to take the lessons Miss Bliss is teaching them about the stock market and put their money in a risky stock option involving potatoes. The class soon learns that as fast as stocks can soar to high profits, they can just as quickly fall, and as a result, they ultimately cost Miss Bliss a lot of money.