During the "search" she opens the doorway under the stairs and knocks the scaffolding against the hidden door, shutting it/locking it. She frantically runs down to the beach and the cave and momentarily sees the image of Tomas (the clothes resemble the outfit Simon has taken). At this point she does not know Tomas is deformed under the mask, so the image she sees IS Simon dressed in those clothes. Whether this is real or imagined, it's never explained.
9. Simon soon realizes he might be stuck down there and starts banging on the walls. Several days pass. Because of her leg injury, mom is stuck upstairs, and dad, who we know is a hard sleeper 'I'll go, its my turn', doesn't hear the pounding. She's lying in bed, hears the pounding, and hears Simon falling through the broken railing, but of course doesn't connect it. She finds the doll but doesn't connect it with the doorknob game or his disappearance.
Noises lead her to the she where she finds Benigna with a shovel.
10. Car crash incident, leading to the discovery about Tomas and Begnigna.
11. The Medium pays a visit and discovers the "ghost children". She later says that they aren't truly spirits, but something "left behind" that only certain people can see. In her trance-like state she can see the past (the evidence of the lighthouse and the changed furnishings of the house). However, she does not see Simon because Simon has died in the cellar and for whatever reason she never even goes downstairs
12. The Medium tells the mother that people who are close to death or are dying can sometimes see things regular people can't.
13. "Doorknob Game" - Still looking for the answer to the doorknob mystery, she discovers a clue left behind by Benigna and discovers the bodies, but she still has not solved Simon's game.
14. The husband says he will no longer stay in the house. Laura asks for just two more days to "say goodbye". She takes many many pills through the course of the next 48 hours. She restores the children's room and the dining area. .
What happens next is open for discussion whether it was imagined or real. In her state of shock (after discovering the bodies), anything could have really happened. She discovers the children (knock knock game from her past), gets locked in the room under the stairs, discovers the secret door, goes downstairs, perhaps now in a trance state does not notice the broken railing, goes down and imagines she's found Simon. Again, what the Medium says is that sometimes a trace of something gets left behind, and people who are close to death can see this.
She awakens from her trance state and finds his corpse and realizes what really happened. She takes his body back up to the kid's room and overdoses on her pills, she removes the medal her husband gave her. She "awakens" to find the other children and her son, Simon and begins to read them a story.
Story ends with Laura's husband at her memorial site with the names of the children, Tomas, Laura and Simon. In the upstairs room he finds the medal left behind, smiles. End of film
The entire film functions without any supernatural occurances. The entire end sequence was either imagined, brought on by stress and high amounts of psychological drugs, or if you prefer, leads to a "happy ending" she imagines in her last few minutes of her life.
因为想剧透又怕你们缩所以放了英文版