When George's mother buys an antique chair at an auction, the Five don't expect it to be the start of an intriguing new adventure. Very soon, however, they discover the chair's valuable secret; and when someone breaks into their house in the middle of the night, it becomes clear that another person knows that secret too. The Five have to do some dangerous detective work to discover just who this 'mystery man' is and prevent him from stealing what isn't rightfully his . . .
