Minor Plot hole: The assassin who is sent to subtly kill Dr. Martin Harris in the hospital sees fit to snap the neck of the nurse taking care of him. If he had to be subtle, he failed by snapping the neck of the woman, and if he didn't had to be: why poison Harris instead of snapping his neck too ? Either way, the assassin's plan does not make any sense.
Major Plot hole: Everything could have been avoided if the company Martin Harris was working for did not let him alone in a hospital for four days instead of taking him in.
They had to know he was somewhere in a German hospital and since they already sent the second Martin Harris as a replacement, both of them could not use the same fake identity without raising some suspicious eyes. The best and only option for the company was to not let the original Dr.Harris alone.......but they forgot about him.
Plot contrivance: Dr.Harris has a severe memory loss during most of the movie. He only remembers his impersonation training as Dr.Harris; thus making him believe he is the real Dr.Harris. But why is he not concerned by the fact that he remembers NOTHING prior to his recent training ? He thinks he is married to Liz, but can't remember his marriage with her, or when he met her, or his own complete childhood. With this condition, he should have noticed something was wrong with his head if he could only fetch information from the most recent year of his life.
Plot contrivance: At the end of the movie, Dr.Harris remembers everything back again. Why is he against the assassination plan ? He was ok with killing people for most of his life. The only reason he was against it for about a week was because he was impersonating someone else. But when he did get back his old personality, why didn't his old inclination towards the plan come back?