I want to see if anyone on this site can design a story of the world turning upside down, with only a small glimmer of hope for humanity.

Examples:

• An intelligent alien species has descended upon our world.  A small group of kids hold mankind's last hope.  Can they save the Earth from certain destruction?
• The gods have been angered and intend to bring Judgment upon us.  But one man seems to have evaded their wrath.  Can he bring peace to the world once again?

It doesn't have to be an original story, nor do the characters, but put some thought into it regardless.