I'm searching for this fic where Jared and Jensen are investigators working together under-covered in a closed community that only accepts gay couples. One of the residents was murdered, Jack Abel's husband if I'm not mistaken.
As one of the rules of living there all the residents take part in a sort of swingers party every now and then. Jared and Jensen don't like each other very much in the begging but grow found and protective.
I can't remember the author or title.