Personal Opinion on the door knob and the debate
I see how this film attempts to mix the supernatural and reality card but to me the real puzzler deals with the doorknob itself and the doll pointing to more of the real part of the story.
Now i firmly believe it was Simon who was dressed up as Tomas and locked him mother into the bathroom and went down to Tomas' little house to hide. I can also see that it was possible he set the clues up to lead her there but i see the arguments.
As someone who even as an adult was in that house, i know for damn sure i would have been running around exploring the place, but the two clues of the doll and doorknob pose some questions as to was it possibly for Simon to handle it
I see it completly possible Simon found the hiding place of the child dolls and removed his mother's to use a clue hoping she would remember where the hiding place was and go look for it, but it was placed in Simon's bed. Not really a good starting place for the game to begin if he started it with locking his mom in the bathroom. I could see the argument he expected her to run in his bedroom to find him and find the doll, so this one i can see the other side but the other leads more room.
So we have this hidden door in the closet with a detachable knob that is needed to open it from the outside. Now this is where i call Simon couldn't do it on his own. If i was roaming around a house exploring and found a detached knob, i probably wouldn't expect it to go to a secret door as much as it was a broken one or go look in a closet till i found it.
I think this points to one of two alternatives:
1. Benigna gave it to him to show him where he son was
2. Tomas' ghost gave it to him to show him where he was kept
I really can't buy into Simon finding the doorknob itself and then the hidden door it goes to in a place that was already probably cluttered when he found it. It makes much more sense someone told him where it was, whether it was the actual lady or a ghost, is still allowing the viewer to take a supernatural or logical side.
Plus i'm assuming when it was used to hide Tomas, it probably had a pretty good hiding spot, and Benigna and the ghost of Tomas would probably be the only ones to know where it was, and could have lead Simon to exactly where it was. I do think though he may have left it as a clue since he wasn't the sharpest knife in the drawer. After all the hidden doorknob of a secret door in the closet doesn't seem like the best clue to use in a scavenger hunt game. I'd probably have gone with something from the closet for her to see the creaked door, but if Simon wasn't playing with a full deck, he might have assumed his mother knew about the secret door from her childhood. But i still don't buy him finding it without the help of someone like Benigna or Tomas
I refuse to argue on IMDB until the general populous actually uses their brains