Becka, age twelve, and Boomer, age eight, are sisters whose parents are in the middle of a trial separation at Christmas time. Becka, a precocious computer hacker, has become cynical and withdrawn. Boomer tries to be the peacemaker, eternally positive and anxious for all around her to be happy. Their parents, Dean and Irene, both child therapists, disagree on how to deal with the problems of their own children. While taking her sister to the mall to see Santa, Becka is goaded by her hacker friends into telling Boomer that there is no Santa, and when she does, this threatens to ruin Christmas for the family. While Dean and Irene try to deal with the fallout, the magical and mysterious Mrs. Rosen, comes into everyone's lives and begins to change the equation. She challenges Becka to prove there is no Santa by using her computer to see if she can't find him hooked up to a network somewhere. Becka, feeling more and more remorseful over what she has done to her sister, is intrigued by Mrs. Rosen's challenge and by the end Dean and Irene have reconciled, Becka has a brighter outlook on life, Boomer gets her Christmas wish, and Santa�well, of course he's real. "