After a series of mishaps and misunderstandings, Greg is accused of stealing a valuable antique, which is actually his dad's, and then caught trying to use a fire extinguisher to prank his classmates. This leads to his expulsion from school, leaving him with a bleak future and a desperate need to clear his name.
This cliffhanger serves as a great way to end the book, leaving readers wondering about Greg's fate and what he will do next. It also sets the stage for the next book in the series, "Diary of a Wimpy Kid: Dog Days", where Greg is forced to attend summer school and deal with the consequences of his actions.