At the beginning of the play, is angry with his niece Abigail because?

I think that you are referring Reverend Parris. He is pretty upset because Abigail is caught dancing in the forest dancing naked around a cauldron. She is smeared with animal blood as well.Yikes! This is about the worst thing anybody could do in a paranoid god-fearing town like Salem. Rev. Parris sole concern is himself. A bunch of girls practicing "witchcraft" under his watch does not look good for him.