"High Tension" could've been and would've been better if it didn't go the dual personality route. The whole movie we were led to believe that a strange man (Philippe Nahon) came to Alex's family's house and killed them all. We were led to believe that Marie (Cecile de France) was able to hide from the killer and then pursue the killer who'd kidnapped Marie's friend Alexia (Maiwenn). Then, when the movie was about to conclude we found out that Marie was the killer the whole time and she only imagined (or was taken over by) the other personality. That would've been a nice twist except:

A.) I've seen that twist too often ("Fight Club" did it best).

B.) It was hard to reconcile what really happened with how Marie imagined it.

Marie saw another man, she hid from this man, she ran from this man, she pursued this man in a totally different vehicle, she fought him and presumably killed him. I can stretch my imagination and reconcile much of it, but I can't reconcile the two different vehicles. How could she have been driving the Jeepers Creepers truck with Alex in the back as well as the yellow sports car (unless the yellow sports car didn't exist)?

"High Tension" was a decent movie, but it would've been better if it had honestly stuck to the thread it was on: a determined woman pursuing a kidnapper/killer to rescue her best friend. Not to say that the dual personality angle wasn't good, it was actually quite cool because who'd expect a woman to be a crazed homicidal maniac, but the execution wasn't the best.