And then they heard a creaking voice behind them. 'Get out of here!' said the voice. 'Get out!'

Over on Billycock Hill the Famous Five have set up camp and are ready to explore. They are thrilled to meet Jeff, the local pilot, but when two planes are stolen overnight, their new friend becomes the accused. Something mysterious is going on and the Five want to solve it. Why would Jeff steal a plane - and if he didn't, who did?