The movie Torchwood makes me think of is Blindness -- this horrendous event that the populace is in no way prepared to cope with, the panic, the helplessness. That movie ends with the beginning of the return to normalcy, and Torchwood seems headed in the same direction. The ending of Children of Men is more problematic (and more effective, IMO); the ray of hope we're given comes with a big question mark attached. But all three share that same heavy atmosphere of despair, so difficult to achieve fully and remain credible.