His insights had a solid factual foundation. Consider a late scene in which Cross needs to deduce a computer password. The fact is, passwords are rarely obvious. Clearly, the number of permutations is enormous. The result is to cheapen the quality of the mystery, making me wonder why more time wasn't invested in coming up with ways for the characters to creatively solve the puzzles.
Omniscient detectives are usually symptomatic of lazy writers.
Similarly, I was a little disappointed by the movie's big swerve. It represents a wholesale change in the nature of the film, prematurely terminating the main plot before I felt it had been fully plumbed. The better mysteries have enough red herrings that no single possibility clearly presents itself. I've been intentionally vague about the actual plot of the movie, for fear of giving too much away. Potter is the disgraced agent who had been responsible for the girl's welfare.