It's quite the original premise, but, unfortunately, ordinary in its execution.
Isabelle Huppert is her usual, fantastic self, but eventually the walls close in on her, too, and no amount of acting can transcend the clunky construct.
The film is so implausible that it never quite sinks the hook, and that's too bad, because it really could have been something spooky and haunting.
“Of all sad words of tongue or pen, the saddest are these, 'It might have been.'”