In this book Harry is in his 6th year. This year Harry's scar does not hurt at all any more. It turns out that Voldemort learned how to close his mind, what he is doing to close his mind is called Occlumency. In this year Harry takes personal classes with Dumbledore. The reason for this is because Harry needs to learn about Voldemort's past. He does this by watching old memories from people who died or want to help. In one of these memories Harry and Dumbledore find out find out about Horcruxes. A Horcrux is when someone splits their soul into how many pieces they want to. Voldemort has seven Horcruxes. It's up to Harry and Dumbledore to find them and destroy them. After that they have to go after the last bit of his soul left in his body. Oh, and someone dies in the book...