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! They take to the skies on board Mr Helium's very own balloon in order to catch the cheat. But will the detectives become victim to the dastardly villain's dangerous schemes and dirty tricks, or will they blow his plot sky-high?