Max and Maddy are on the trail of a criminal who'll stop at nothing to sabotage Mr Helium's trans-American hot-air balloon race. The prize is a gold balloon worth one million and one dollars, and all the money raised by the race is to go towards the Home for Children Whose Parents Have Disappeared in Balloons – so there's a lot at stake! Will the detectives be able to blow the dastardly villain's plot sky-high?