The first 45 minutes are anarchic, witty and spectacularly inspired. An asteroid is going to wipe out all of humanity and sends people into hilarious bad behavior and ambivalence toward their impending doom. Then the film trades in its aggressive dark comedy for a cutesy romance that practically derails the whole film. In fact for a good portion of the middle act,it's a generic rom-com that ignores its own premise. Keira Knightley's character is an irritating quirky type that comes across demented when that's obviously not the intention and spending the remainder of the running time with her is suffocating. It's a shame the film lost its way after a great first act, because this could have been a classic, as opposed to just forgettable.