I think it was Jared who's a doctor at a clinic that specializes in heart repair: if your heart is damaged by a break-up, the death of a loved one, even just extreme stress or something, the doc will open you up and sew the damage with specially chosen string or gears. There's a serial heart-stealer who's going around grabbing half of peoples' hearts, and Jensen gets his stolen. A cop is investigating Jared as a suspect, but he ends up giving Jensen half of his own heart because he's got a crush and Jensen's heart is too mangled to survive half on its own. Also Misha is a homeless? at least openly uncaring about where he spends his days guy who hangs out int he neighborhood and at the clinic.
Thank you! Adore this fic. On the subject, anything in the ballpark of this, fics where the heart can be interacted with, in any fandom, would be sweet. I know of two in Torchwood that I'll give if anyone cares.