Hotch/Rossi adding Reid

Hi,

I mentioned a threesome fic I read recently on another com, and was asked about it, but I failed completely on the bookmarking...

Hotch and Rossi are in an established relationship, and I belive Reid approaches one or both about teaching him about sex.  They agree and arrange to spend the weekend together.  There is (I believe) a pool involved at some point, but mostly I remember it as being a very sweet and understanding established couple introducing a shy friend to the more pleasurable aspects sex.