If you want this movie to be an exciting thriller a la Bourne Identity, then I am afraid you will have to look elsewhere. This film is largely a character study of a hitman who is attempting to re-discover his soul and as a result save it.
Played by George Clooney, the film presents us with a cold hearted individual who is very proficient at killing. A man that is totally one dimensional, he exists without any meaning or purpose. He is the embodiment of a nihilistic existence. The film begins with a scene which seems to imply that the character is a sociopath, yet as the film progresses, we see that he is indeed a man with a conscience who has chosen a path of evil.
The action in the film is mainly due to the fact that another criminal organization wants to kill this hitman, either for reasons of retribution or some kind of debt. Their incompetence seems to make the Clooney character probably more adept at survival than he really is, but again this is all peripheral to the nature of this film. This is not an action thriller, but the story of an evil man attempting to find redemption and meaning in his life.
The hitman meets two people in an isolated Italian village which seem to spur some kind of personal examination of his existence. The first is an old Italian priest that seems to take an interest in his salvation upon meeting him, and a prostitute he was frequenting in the village who falls in love with him. The film explores how love is so difficult to achieve for this man, largely due to his inability to trust, which in many ways has been keeping him alive in a treacherous business. Nevertheless, he decides to reach out for it, and get out of the killing business beginning with a refusal to complete his latest assignment.
This film is one of the best examples of a film exploring the existential and moral conversion of an individual drowning in a sea of evil and nihilism, and instead attempting to find meaning and love in its place.