Grandmother's House (1988)

David and Lynn have just lost their father. Now orphaned, the youngsters are sent to live with their grandparents in a beautiful victorian mansion. But no sooner than boarding the coach bus scheduled to take them to their new home do strange things start to occur, initially in the form of a mysterious woman who seems to appear and disappear in the blink of an eye. It’s not long, however, before murdered bodies are found in the area and, to make matters worse, David becomes increasingly fearful that his doting grandparents might be involved in the killings.