The boy in the  burning house by Tim Wynne Jones
Published by Usborne

Life has been tough recently for Jim, his father has mysteriously disappeared and things are only just getting back on track when he is attacked by a crazy girl.   Ruth Rose has a wild story to tell about her stepfather, the saintly Father Fisher.   Trouble is she needs someone who is going to believe her and story and to help her prove it.   After much convincing Jim begins to see that Ruth Rose might be telling the truth and so the pair find themselves on the trail of a murderer and caught up in a dangerous web of secrets from a very frightening and unsettling past....