As Harry, the devil had no claim on his soul but in the end he got him to remember who he really was by making him meet all his old friends etc. now that he knew who he was Satan could lay claim to his soul.

I didn't entirely understand the reasoning behind the his plot, but also assumed he needed to corrupt johnnys new "clean" soul (harry).
I disagree with the poster who says Louis wanted nothing to do with Harry. At the very end of the movie when the credits end and the elevator reaches its destination, you hear a louis' voice saying both "johnny" and "Harry."

I get the impression that Johnny's going down, but Harry is really an innocent victim here who gets kidnapped, murdered, sacrificed and used as a soul-shield. I don't think Cypher is interested in Harry.

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