I like it when plots don't present all explanations in a clean and direct way. But I feel something is missing. The ending seemed rushed, as if some expected scenes were cut out.

First thing is the old woman. Ok, she's a ghost, that makes it pretty clear that ghosts exist and are communicating. So, is the voice of the mother real too? Is she a ghost talking to her son and then to Verena? Or was she just under stress? I doubt it, as nobody ever talked to her about the old woman, so she couldn't imagine that.

There are some scenes where she's really very stressed, but it falls on that odd situation. If she's hearing ghostly voices and is being seen as crazy, then it's acceptable she'll get in that state.

Another is the mother death. When her voice is first heard, my feeling was that she was trapped on the wall and was asking her son for help without letting the husband know it. Indeed, the movie has some references to this: the cat and the dream on the end. It's very doubtful she was trapped because the movie ended with no plot twist evidencing the husband is evil.

In the end, I understand that the boy talked because he was asked by his mother to expect for a woman to arrive who would care about him. So, while there was none, and while those nurses only saw the family as work, he kept silent wanting, and stimulating new nurses to come. Once she cared for him as her son and for the husband as a husband, then he accepted her and talked. Is that right? Could we consider that the ghostly mother herself accepted Verena as her replacement and her son knew it?