Emily, a pianist at a London private girls' school catering for gifted young musicians, is saved by her imaginary brother, Jimmy, from committing suicide, by drowning in a pond, because of bullying instigated by a new girl, Belinda. With the help of the girl's world-famous pianist granny's imaginary friend, Jenny, who shows Jimmy how to enter the hippocampuses of the brains of the bullies who were once Emily's musical friends, things are turned around. Because of problems revealed by the girls' memories stored in their brains, visible to Jimmy and Jenny, Emily is able to help, and win back these friends and together they form the Roo Club (tenets: 'Forgive, Help, Love) to aid girls with problems. Soon the beautiful half-Italian Belinda, becomes the isolated one. What, Emily wonders, should she do when Belinda calls her, asking to meet up beside the very pond where she intended to end it all? Again, she turns to her wise imaginary brother for help. And who, really, is the mysterious Jimmy?