On a class trip to the Cornell Mission, The Code Busters learn about Hippolyte de Bouchard, California's only known pirate. Now the Code Busters are on the trail of a new prize: pirate gold! But with a fortune at stake, the codes are bound to be hard. Will the Code Busters be able to figure them out, or will this mystery prove to be too difficult to solve? With fun interactive codes to solve throughout, children won't even realise that when they join the Code Busters on their next adventure they are also learning vital problem solving skills and maths.