Remember that passage in the Book of Revelation when the archangel Michael kills a bunch of possessed, tiny-dentured zombie types with a machine gun at a rundown desert diner owned by Dennis Quaid? Us neither. Still, that's pretty much the entire plot of this dull horror movie. The problem lies not with any lack of interest on the part of the B-lister-filled cast. Paul Bettany sells the hell — or, perhaps, the heaven — out of his gun-toting angel and Adrianne Palicki from Friday Night Lights is convincing enough as the heavily pregnant mother he has defied God's orders to protect. Meanwhile, Kate Walsh deserves some sort of medal, or another zero on her paycheck, for gamely portraying a woman who, in one of the film's more memorable sequences, narrowly escapes being dissolved by pus. Alas, after a brisk start, the script turns out to be a rough and humorless beast slouching its way towards utter ludicrousness. "The future has been unwritten!" intones Bettany at one point. But there are times when Legion barely seems to have been written at all.