After defeating Lord Voldemort, Harry is ready to go back to Hogwarts for his final year in the new and peaceful world. Although his greatest foe is no more, Harry's troubles are not quite over. He's shocked and horrified when he watches Professor McGonagall kill Colin Creevey's little brother Dennis. While everyone gets their lives back on track, he discovers hidden corners of the magical community and a powerful secret society that will achieve its goals no matter who stands in its way.