He gave me so much to remember

Their love was the purest and rarest kind of love. They knew that their love was one of those things that lasted forever. Harry was oxygen for Louis. He was his heart beat. He was his home.
Until one day he left, and took Louis' soul with him and returned as an entirely different person. Louis couldn't understand why his Harry turned into something he never expected him to.

Will Louis ever understand what really happened in Harry's life? Will they find their way back to each other?