It were good, Mrs B screamed when the first alien face appeared, but - I know that we are not meant to actually ask questions of the mechanics of sci-fi, and that it was just light entertainment, and I don't want to sound like Comic Book Guy...but, why didn't he just grab all the people, take them to some far of planet of friendly aliens and leave them there to live out their lives quietly? That way history wouldn't have changed - people on earth wouldn't know they survived and all would have been happy.