Cry in the Dark  (English, Paperback, Shulman Dee)

A time-slip ghost story based in the gritty reality of Victorian London. Ben breaks into the empty house next door and discovers a family of children suffering at the hands of their drunk and abusive father. Ben has to befriend someone from the family's own time to contact their relatives and rescue them, hence a combination of modern sleuthing and contemporary letter-writing to achieve the desired end.