A thoroughly engrossing read that I've just finished. Haven't been able to do much else for the last few days, other than be enthralled by this. Thanks to @cachondo for pointing it out to me.
Title: The Second String
Author: Eider_Down
Summary:
Everyone knows Dementors can take souls, but nothing says that they have to keep them. After the Dementor attack in Little Whinging ends disastrously, Harry must find a place for himself in a new world, fighting a different sort of war against the nascent Voldemort.