How many of us out there are having sex with people we are ashamed to introduce to our friends? Carrie thinks Mr. Big is keeping her a secret, while Miranda discovers a secret about her new boyfriend. Samantha has never been discreet with anyone she's ever slept with, and Charlotte divulges her past love affair with one of God's chosen people.

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.