Famous Five #2-Five go adventuring again by Enid Blyton

Look! That’s the thief?
Come on, we’ll soon get him!”                                                                                                                                         

When the five discover an ancient map that leads them to a secret passage, they can’t wait to follow it. But then Uncle Ouentin’s important papers go missing and a real treasure hunt begins.
George – and Timmy – have their suspicions, but can they all work together to outwit the criminal?