Hermione researches the plight of the house-elves, who are slaves to their masters and must do whatever their masters require. The house-elves are uneducated, and unable to argue or think for themselves. They are kept as unpaid workers by wealthy wizarding families, and their treatment depends on the mercy of their masters. Hermione finds this despicable, and she works throughout the book to liberate this oppressed minority. The enslavement of the house-elves mirrors the enslavement of wizards, good and bad, at the hands of Lord Voldemort. Whether by swaying them to follow him willingly, or by placing them under the Imperius curse to cause them to follow him without knowing it, he gradually pulls much of the wizard community into his power, to work for his whims and to perform his malicious tasks toward the goal of wiping the world clean of all but pure-blood wizards. Dumbledore leads the crusade against wizard enslavement just as Hermione leads the one against house-elf enslavement, and hence, this book protests enslavement on both grand and small scales.
In this story, almost nothing is achieved by a single person alone. Harry, brave and resourceful as he is, could not triumph in the Triwizard Tournament alone. Hagrid and Moody helped him prepare to get past the dragon; Cedric and Dobby helped him decipher the golden egg and rescue his underwater victims. Although Harry gets through the maze with his own ability, he could not have escaped Voldemort without the protective charms of his wand's affiliation with Voldemort's wand. Furthermore, Harry is marked by his parents' sacrifice to keep him alive, so that even when he appears to be doomed, he often is protected by a connection to them. Almost nothing that Harry does in any of these books is achieved alone; he approaches challenges with courage and a basic groundwork of skill, but the friendships and connections he has made along the way enable him to succeed. Harry reciprocates this aid within his community. He encourages Hagrid to return to teach, and he lets Cedric know about the dragon. He also lends Moody his Marauder's Map. The boarding-school setting of Hogwarts allows for an insular, tightly bound community in which each person's actions affects somebody else, and this connectedness is a key factor in the successes of these stories.
J.K. Rowling portrays the comings-of-age of her main characters. This novel shows the largest development from one year to the next. Ron, Harry, and Hermione have entered adolescence. Harry is hesitant to tell grown-ups that his scar hurts, as he is concerned about his self-image. He is also, for the first time, very aware of Cho Chang. Ron is more self-conscious than ever about his lack of money and his shabby dress robes, and he is defensive about Harry's fame. Ron is also more sarcastic than ever in his scorn for Percy. The first feelings of romantic attraction are stirring throughout this book. Sexual tension between Ron and Hermione causes numerous arguments in this book, and it is clear that much of the book's events reflect subtle changes within the maturing process of the characters themselves.