I am looking for the title of a movie and I've searched so thoroughly but to no avail. I've watched it recently (3-4 months back).
It's about a girl who discovers that her psychiatrist is actually a killer or something of the likes but before that she suspected her neighbour and broke into their house to find his dentures but they landed in a pile of newspapers and the neighbour woke up.
When the girl finally realises she can find proof she makes her mom stay in the room and distract the psychiatrist (who is an old man) and goes into the basement to look through documents, and true enough she finds documents of how the psychiatrist had interned at her house (which was a mental institute or a troubled youth centre?) and had gotten beaten up by some patients and he has come back for revenge (I'm not sure why).
When he finally stops the mother from talking he excuses himself to the toilet and he doesn't ask where but miraculously knows where it is and he gets confronted by the daughter and the mother when he comes out. The man in the wall has once cut off the power supply and managed to seriously injure the psychiatrist. The mother and daughter hide in the toilet while the psychiatrist looks for a saw (?) to cut open the door.
I also remember in one scene the daughter uses a cheese grater to rub against the psychiatrists face. And in the last scene the mother is getting choked by a telephone wire by the psychiatrist and the daughter was knocked out. But the man living in the walls taps her and she wakes up and he passes her a knife or a taser, I can't remember.
I'm so sorry this is in bits and pieces but it is what I remember. Also the man in the walls has crazy hair and is always watching TV. Thank you in advance!