Four men, sheltered deep underground, were all that remained.  There they had waited for 30 years for the zombies to finally go away, but they hadn't.  With the food gone and the water running dry, they knew their days were at an end.

But yet they had hope.  They hoped that somewhere, somehow, someway, somebody else had survived.  And if they had, then maybe someday they would find this place where the four men had been hiding.  So each determined to leave behind the one thing he believed to be the most important to beginning life anew on a planet with so much potential.

The Scientist among the four left behind detailed instructions on the basic forces of the Universe:  Nuclear strong and weak.  The electromagnetic positive and the electromagnetic negative.  And gravity, the least understood of them all.  Everything necessary to create technology once again.

The Businessman left behind the knowledge of profit and loss.  Supply and demand.  Buying low and selling high.  And the cost of opportunity.  Everything necessary to create economies, both big and small, once again.

The Philosopher left behind knowledge of all the world's great religions.  The Bible and the Koran.  Buddhism and Hinduism.  And even the belief of not believing at all.  Everything necessary to understand all those things that cannot be understood.

The last of the four was a Janitor, who knew how to clean.  He left behind a bottled filled with a virus.  It was the virus that would turn one into a zombie.  And on that bottle was a tag.  And on that tag were written but two words.  And those two words were, "The cure."