Louie, who was abandoned at Chipchase's Travelling Circus as a baby, dreams of becoming a 'Showstopper', but Mr Chipchase keeps her hidden, tucked away in the ticket booth. But Louie has been secretly practising her act; the tightrope and dreams of being the 'girl who walked on air' - she just needs to be given the chance to shine. And the circus needs her too - Wellbeloved's rival show is stealing their crowds. Desperate, Mr Chipchase reluctantly lets Louie perform. She is a sensation, and gets an offer from the sinister Mr Wellbeloved himself to perform - over Niagara Falls. But nothing is quite as it seems and soon Louie's bravery is tested not just on the highwire but in confronting her past and the shady characters in the world of the circus.