Unseen, impregnable, the strange war engine of a foreign power hovered over America, waiting the fatal moment to hurl death upon a thousand cities and towns. Foredoomed to destruction and desolation before the ravaging hordes of the Yellow Empire, bleak despair gripped the nation's millions. And then men held their breath in agonizing hope—as Operator #5, single-handed, seized the last grim chance to save the United States!