It is the holidays again and Joe Robinson and his cousins are back with Granny in Muddlemoor. The problem is... Muddlemoor is a hotspot for crime. When Joe, Tom and Pip discover that a dangerous gang of robbers is hiding in the local area they start an investigation straightaway. But hang on a sec. Granny's Book Group seems to be acting RATHER suspiciously. For one thing they NEVER talk about books and for another thing they keep going on about a local bank. Oh no! What if Granny's Book Group are the true-life bank robbers? There's only one thing for it. The cousins must stop Granny getting arrested, even if it means putting themselves in danger.