Max and Maddy Twist's parents were once famous, international detectives - before the evil Professor Sardine ruined their careers, that is. Now they run an ice-cream parlour, and it is the services of their crime-busting Cluedo-champion children that are called upon. Mr Huffendort, a rich Swiss banker is very worried about a series of raids upon banks, carried out by a team of highly-trained St Bernard dogs! Who can be the criminal mastermind behind this evil and cunning plot? It's time for Max and Maddy to pack their hats, scarves and various disguises, and fly to Switzerland to find out ...

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?

Billy, Nicola and Mr Gopal are off to India in a flying boat to solve a baffling mystery! The gum that comes from the wonderful bubblegum trees that grow in the Indian jungle has not been delivered for two months. Without this secret ingredient, there'll be no more Gopal's Best Pink Bubblegum, and even more importantly, no more Bubblegummies - the people who live in the trees and harvest the gum. It's not an easy mystery to solve - and soon the friends are involved in a bungee-jumping, tiger-trouncing, woodcutter-walloping, bubblegum-blowing adventure!