Luxurious, expensive Apartment 3B is for sale. Many want it, only one can buy it. Its owner, Liz Lacey, successful artist and darling of the jetset, is about to make dramatic changes in her life. ''Apartment 3B'' is the enthralling story of Liz Lacey and of the men and women who come to view her apartment: sophisticated, cosmopolitan Lainey Conroy; globe-trotting media personality, Hugh Cassidy; gentle, determined Claire Moran who has triumphed over adversity; ambitious but tender-hearted Dominic Kent. And Cecily, sister-in-law to Lainey, who will stop at nothing to prevent Lainey from acquiring the apartment.