At the end of the movie, Josh is hypnotized to go into The Further to save his son. He brings the kid back, only to be possessed by a spirit himself. He kills Elise and the movie ends. Why does this make sense? Because:
Throughout the movie, there’s a ton of dialogue about Josh’s childhood, in which a spirit haunted and tried to possess him. Josh remembers none of this because his mother (Barbara Hershey) enlisted Elise to hypnotize him. This is why Josh doesn’t believe Elise when she tells him about his son’s being taken by the spirit. This is a variation on the traditional modern haunted-house movie in which the husband never believes what’s going on until it’s too late. In this case, Josh’s refusal to believe and his subsequent estrangement from the family is due to his childhood hypnosis being so strong.
Therefore, it makes perfect sense that Josh would be taken at the end, because he was the target all along! The kid was just the bait to bring Josh into The Further, where his body could finally be possessed. Hence the title. OK? Everybody got it now?
Now, whether you like the ending or not is up to you. But you can’t say it doesn’t make sense or that it comes out of nowhere. It’s all right there in the movie itself. I just explained it to you. Now stop saying that the ending sucks.
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