Buffy, Spike and Oz form a threesome and Scoobies get mad

Looking for a fic where Buffy and Spike end up in a threesome with Oz. I think they form some sort of pack together. The scoobies are not happy with it especially Willow because I think Oz leaves her for them. I also think Willow and Xander follow the three of them at some point to find out what is really going on. I know it isn't much to go on but cannot remember more just that Buffy, Spike and Oz end up together.

Google sent me to something called The Wickedness of Oz by maryperk. I can't get in without an account, so that's a link to the reviews page.

That is the story thankyou!