Volume 2 of The Forbidden Circle, a series of erotic stories for women (which men are welcome to read).
This story involves explicit sex between two men and one woman, including oral sex.
When Steve gets chatting to his friend Nick, the subject of swinging is one that often comes up. However, both Amber and Karen, their wives, are against the idea.
After a time Nick announces that he and Karen are getting divorced. Amber's reaction to this is that it leaves the way clear for a threesome!
This event very soon takes place during one of the steamiest sessions ever known in a hot tub. Then, when it is finally all over, Amber finds her own way to thank Steve for introducing her to this new experience.