The Harry Potter and the Chamber of Secrets book included a significant clue that Harry was a Horcrux, but the movie left it out. This had a lot to do with the clue's subtle nature and the fact that the now-important passage would have seemed only slightly curious when audiences first read it. However, when returning to the second Harry Potter book after the series was completed, it becomes clear that Harry felt a powerful connection to Tom Riddle's diary long before he ever learned that he was a Horcrux himself.
