All begins at the end (Destiel)

Dean from 2009 is stucked in the year 2014, where the Croatoan virus contaminated most of the population. The Dean from 2014 goes away for weeks on a mission. 2009 Dean discovers a Castiel, drugs addict and broken from the inside.
Dean barely recognises him.
He wants the old Castiel to come back and he is going to do anything to help him.