Imagine, if you will. That the fate Future!Castiel's "fearless leader", Dean Winchester, had supposed for him, as well as his fellows Rick and Risa... Wasn't fulled. That he did NOT die in that sanitarium. Instead, Cas escaped. His only thought, "Dean!". Find him. Help him... Save him, again, even if Death were a certainty. Instead, Cas finds Dean... Already dead.
And, as he saw no future without Future!Dean, Cas grabbed Past!Dean's ankle as Zachariah took him home and ended up back in 2009. But... Did the hippie ex-angel make the right choice?
(Supernatural fanfiction - Untold number of more chapters to sporadically come)