And Alex Makes Three

Ann and Rachel met in the story Ravishing Rachel, though this book is a sequel to that story it also stands alone. Ann and Alex have lived together of some time in an open lesbian relationship. So it was a bit of a surprise to Rachel when Ann took her home from the gym for a soak in her hot tub, aware of her involvement with Alex, but understanding she was working out of town. Alex returns home a week early.
The three of them share an awkward moment in the hot tub until Alex breaks the ice and moves in on Rachel. Ann is forgotten and Rachel and Alex become infatuated lovers. Ann, having been left high and dry from a series of unfortunate events, Alex out of town on another job and Rachel having to go to care for her mother for several weeks. Ann is feeling abandoned and pines away remembering that day in the hot tub dwelling on what could have been and wishing it could be resolved.
Then as if an act of fate, Rachel comes to Ann's and tells her she and Alex have had an terrible argument and Alex had left Rachel by herself. Ann and Rachel patch things up and decide to do something they had often talked about but never followed through on. Ann had thought that Rachel and Alex might be likely candidates for a menage a trois but that crashed and burned before it ever got off the ground.
So with renewed vigor, Ann, along with Rachel set their sights on a likely candidate. Resulting in very strange results.