Literary Elements:

Plot

Foreshadowing

Imagery

Harry Potter and the Chamber of Secrets has various and many interesting plot changes or twists:

1. Harry Potter finds the diary of Tom Riddle. This interesting little diary consists of a magical spell that the person's soul is embedded in the book and this allow Harry to talk to T.R. Knowing that Tom was at Hogwarts when the first attack of the seprent was taking place and this allowed Harry to ask Tom. However, instead of telling Harry about the events, Tom showed Harry a first hand account through vision of the event. In this vision, Hagrid was the one letting SOME sort of beast rip through the school.
2. As events progress, Hagrid is takin' to a wretched prision feared by all wizards, Azkaban, where he is to stay until the monster is captured. While being takin' away, he tells Harry and Ron, whom at the time were under a cloak of invisibility to follow a line of spiders, had they seen any. Over a short period of time, Harry and Ron come across a group of spiders, which lead them deep into a eery forest, where they met the creature Hagrid was keeping. Not a seprent, but the worst enemy of a seprent, a spider. This spider told them that Hagrid did not commit the crimes, and that monster was still inside Hogwarts searching for the blood of those who were to be thought impure of true wizards blood (meaning a mix between wizard and human).
3. As the story progresses, Harry comes across the Chamber of Secrets, where he ironically meets the one who had released the monster on the school, none other than Tom Riddle himself. Tom had set Hagrid up inorder to be able to get out of trouble. Latter does Tom reveal that his name is a alias to his real name, Voldemort, the most feared wizard of all time.