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 ...