Architect and amazing lover Jack, an ideal catch for princess Charlotte, whom she met at many disease benefits, strongly suggest a trio with another woman- the friends are divided if or how. Samantha does it with married 37-year old wine importer Ken Shear; when he tells his wife Ruth, she insists Sam participates in his fantasy, a threesome, to save her marriage. Carrie is surprised nearly everybody has trios, and startled Mr. Big is divorced, from publisher Barbara, who proves a great lady and even interested professionally in Carrie's on the spot invented novel theme -intolerable, as if she were in bed with her and Big- and tells he was the cheater! Irritated to be the only one not asked for a trio by a friend, Miranda answers a couple's threesome ad.