A warm, loving family helps Megan come to terms with major changes in her life, in a sensitive, empathetic domestic tale. Megan, almost 12, has convinced herself that the secret preoccupying her mother is a special birthday gift of a cruise for Megan. She is shocked to learn that Mum's surprise is that she has another daughter, now 24, given up for adoption as a newborn. Planning to marry, Natalie is coming to visit in order to get to know her birth mother and her half-sisters. Everyone is thrilled by this except Megan, who cannot understand her mother's years of secrecy and her somewhat besotted affection for a daughter she has never known. Natalie arrives and Megan sees her secretly kick the family's beloved dog; the younger girl resolves never to accept this newcomer as part of the family. Her conflicting emotions toward Mum, Dad, younger sister Betsy, and Natalie are the focus of the story. Ellis (Pick-Up Sticks, 1992, etc.) creates well- developed characters, not only believable but wholly likable; her deft use of wit is delightful. (Fiction. 10-14)