LOOKING FOR A HP FIC

This time, it's a Snape/Lupin/Black fic. Basically, at first it's Black and Snape tolerating each other and there being a very, very careful balance, with Remus as the balancer. The two of them still can't really handle each other, but it's worked, for a little while with them being very equal about how much time is spent between one of them and Remus. I can't quite remember what happens next, but essentially, something upsets the balance and Snape's outside of it. He's preparing to leave when Remus finally puts an end to it by insisting that they roleplay to get over their issues. Thus, Sirius 'buys' Snape and they spend a night together and yay, it's sexy and wonderful.

... I'm all about the Snape feeling chilled out of the threesome, though. XD That's why I want to reread it.

Anyone know which fic I'm talking about?

I posted this over a year ago, and I'm still looking for this fic. Does anyone know this fic on my flist? Please? Please? Please?