The mystery of the pirate's treasure - Penny Warner

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, kids won't even realise that while they join the Code Busters on their next adventure they're learning vital problem solving skills and being introduced to key maths concepts.