答：where=behind the door, from where =from behind the door我们知道，from这个介词可以这么用的。NCE Book2, Lesson 4 :He will soon visit Darwin. From there, he will fly to Perth.这两句话，如改成一句，则为：He will soon visit Darwin，from where he will fly to Perth....
The little boy hid himself behind the door,from where he could see his mum enter the room.=The little boy hid himself behind the door,from 【behind the door] he could see his mum ...
