Spoilers:
I thought it was alright but the ending was a bit odd.
I get that the guy who was laying down in the room was the "real" killer. However I dont get that whole flashback sequence at the end there?
A friend and I watched it and he told me "its like they show in other movies, where they tell you that someone else was really the killer and they show you the clues you missed that point to that guy being the killer." However the flashback sequence in this movie didnt really show anything new or reveal anything.
That confused us, my friend thought it was trying to show that the doctor was involved with the killer's work, however I thought that wasnt right because if the doctor was in on it he wouldnt have cut his own foot off. But if the doctor wasnt in on it then why was the guy chained in the room panicking when the lights were turned off and the door was closed becaue the doctor would get help and rescue him.
All that being said if I were in the Doctors position I would have tried to get the gun and used the one bullet to break a link in the chain. I would then have used the gun to beat the other guy to death.