Believe (2000)

After being continually kicked out of boarding schools, Ben is sent to live with his stern Grandfather in a small town. Almost as soon as he arrives he begins to see the ghost of a woman around his grandfather's house. He also gets to know a girl named Kathrine and the two fast become friends. They both want to help the ghost who holds a connection to both of their families. As they research the past, Ben and Katherine find out that sometimes all you need to do to help someone is to believe.