knock knock be a film that need a chance . this be what be obviously go to earn hate . this movie seem confuse and accord to other view and people do not really understand what be clearly put out there . this slasher focus on a very dark origin for it killer . the origin be sad and you feel sorry for him and which be a good thing . the lead of this film be not any kid and okay and it pretty damn obvious the lead be the killer or if not the cop . the kid be just the kill that the killer come back to do . now when i watch this movie and i be confuse at first and think about turn it off and but please stick with it and a all the confusion fade and you get a crystal clear picture of why everything happen like it do . if you like movie souly for senseless kill and then i suggest you go find some other ( horrible ) horror film then . this be a film you have to think to understand and and a movie that doesn not make you think isn not worth anything .