What event did Harry Potter take part in during his fourth year?
The tri-wizard tournament.
One main event in "Harry Potter and the Chamber of Secrets" is the house-elf, Dobby, coming to visit Harry to warn him not to go back to Hogwarts. Harry, Ron, and Hermione making and taking polyjuice potion is another main event. Harry finding the Chamber of Secrets and rescuing Ginny is another main event in the story.
The climax is when Harry Potter has to fight Professor Quirrell and Lord Voldemort. Quirrell tries to take the stone from Harry, but suffers severe injuries whenever he touches him. Harry uses this to his advantage by putting his hands on Quirrell's face. Dumbledore arrived as Harry passed out and managed to save the Stone. Quirrell died of his injuries.
Harry Potter goes back to Hogwarts and finds out that there will be a tournament called the Triwizard Tournament. Two other Schools show up to compete in the tournament and a representative of each school is chosen to compete. After each School's representative is chosen by the Goblet of Fire, it does something it doesn't normally do. It spits out another name. Harry Potter becomes the fourth competitor alongside Hogwarts other competitor Cedric Diggory. Eventually…