Lord Voldemort has returned, but the ministry of Magic is doing everything it can to keep the wizarding world from knowing the truth. They appoint Ministry official Dolores Umbridge as the new Defense Against the Dark Arts professor at Hogwarts. When Umbridge refuses to teach practical defensive magic, Ron and Hermione convince Harry to secretly train a select group of students for the wizarding war that lies ahead. A terrifying showdown between good and evil awaits.

Sixth-year Hogwarts student Harry Potter gains valuable insights into the boy Voldemort once was, even as his own world is transformed by maturing friendships, schoolwork assistance from an unexpected source, and devastating losses.

In their fifth year at Hogwarts, Harry and his classmates deal with yet another unusual Defense of the Dark Arts teacher, a disgruntled house-elf, Voldemort's growing strength, and their end-of-term Ordinary Wizarding Level exams, all of which reinforce the depth and strength of their friendships.

When the government of the magic world and authorities at Hogwarts School of Witchcraft and Wizardry refuse to believe in the growing threat of a freshly revived Lord Voldemort, fifteen-year-old Harry Potter finds support from his loyal friends in facing the evil wizard and other new terrors.