In this movie, an alien race gives mankind an "ultimate weapon". It's a small capsule-shaped thing which, when activated, kills everybody within some large radius. One scientist offers to test it on a remote island, as I remember, and remembers that the aliens said it was for "good and evil". The scientist thinks the "and" must be important. He inspects the gadget closely, and sees a small pin in one end of the capsule, and a small hole in the other end. He takes the pin out, puts it in the other end, and when activated the gadget now only kills evil-doers. Problem solved.