i forgot i know its a season 7 eppy. i remeber the name but dont remember the eppy...............................wait is it about the naked guy with killer written on him?

Yes I believe that is the episode. There is an uncommon "strain" of the AIDs virus and the one guy kills the one with HIV in order to protect the others. I think that's the episode though I'm not sure.

Yeah, the detectives get help from Fin's son to track down a person who is killing gay men who have a new killer "strain" of HIV. Liv and Fin find out Fin's son is gay during the investigation in this ep.

That man is killing those men with HIV becuz his brother died from that strand of HIV, and he wants to find and kill his brothers "killer" or the man that infected his brother, and all the men they slept with. It's kind a wierd, but i think it's a great eppy.