This book is by J K Rowling and is the seventh book in the series and in this story, Harry loses the protection that his, Mother gave him.

As it was decided that Harry should move from his residence early and it also meant that the Dursleys couldn’t stay there either.

Then after the Dursleys had left Harry found out what he and the others were about to do and although he didn’t like this plan:

He gave Moody some of his hairs.

As they needed a bit of Harry’s hair for the polyjuice potion to work though there was also some risk involved too.