When Scott and Jack Carter have to stay with their great aunt for the summer they steel themselves for the most boring holiday ever. But then they meet Emily Wild and her loveable dog, Drift. Emily shows them the lighthouse, the castle – and the amazing whistling caves. Legend has it that when the caves stop whistling the castle will be attacked – and that’s exactly what happens!

Priceless treasures are stolen and Emily and the boys are determined to investigate. But how was the treasure smuggled out of the castle? Why did the caves stop whistling? And can the friends solve the mystery in time to catch the thief?