Carrie discovers not only that Mr. Big was once married, but that he and his ex participated in a threesome. Meeting the ex-Mrs. Big, Carrie is disappointed to find her smart, sexy and successful. Charlotte’s boyfriend wants to add another woman to their relationship, and Miranda feels left out. Samantha finds that she has unwittingly become too involved with a married couple.
”You in a threesome? You won’t even wear a thong!” -Samantha