Life isn't easy for six-year-old Rebecca. Her parents are at each other's throats, her big sister is totally absorbed with her own problems, and her uncle is intent on Rebecca taking her medicine. Complicating things further, her health isn't so good and her parents keep her home all the time. Ernest, the bacterium who has become her best friend, hopes to reconcile her parents, but things get complicated when a new virus named Sam shows up and threatens...