It's a swell thriller: a reasonably sophisticated plot, with some neat twists and turns, good camera work, and a kind of satisfactory ending. But just as with the murder story in question, the flaws become apparent at closer examination.
Most important, the characters are not sufficiently presented and explained. The deadly duet shows a very close relation, but not what keeps it so close. It would be easy enough to understand, if they were lovers. Then their quarrel over a girl also makes sense. Since they are not - as far as the movie shows us - their relation remains a mystery.
The same, to a lesser extent, is true about the detective duet. Bullock is not really able to convince with her tough exterior to hide inner wounds, although that should be easy for an actor of her experience, and her male colleague gets no room in the film to show us why he stands her, after what she puts him through the very first days they work together.
Although it's mainly a thriller, I guess this movie would have needed some additional efforts on the drama of it, the emotional processes included in it. Maybe it's all too logical - like numbers.
