if i am remembering this right, Castiel and Dean enter a BDSM relationship. Castiel is a lawyer or a Fed, I think... As time goes by Dean notices that Cas is working on a case that may put Alistair and friends in jail. but Cas and family/co-workers are having troubles finding witnesses willing to speak up. eventually Dean admits to knowing Alistair and later willing to testify for the D.A. ... Alistair and company get wind of this and Alistair almost succeeds in making Dean look as if he was taking his own life... I remember clearly that Dean was drugged and in the bath tub and he was crying saying he was sorry. and Alistair comforts him even as he slits Dean's wrist or thigh...

I think i read it on AO3 and it may have been as recent as last year?

any help in finding this fic would be appreciated.
thank you,
sincerely
jazzy

FOUND - ORPHEUS by sysrae
http://archiveofourown.org/works/2364347/chapters/5220227