Smart, complex thriller that relies mostly on character and behavior, not easy shocks, for it's tension. That's increasingly rare in modern suspense films.
A few questionable twists near the end are the only real weak spots. Ben Kinglsey and Emily Mortimer are particularly terrific (though the whole cast is strong), it's great looking (especially on Blu-Ray, but the regular DVD isn't bad at all), and there's a moral grayness to the characters and story I found refreshingly adult and challenging.
A lot of critics thought the ending ruined the film, but to me it may have nicked it a bit, but it was far from a fatal wound for a far sharper than average, grown-up thriller.