When twelve-year-old Alex arrives at her grandparents' countryside cottage for Christmas, she expects a quiet, boring holiday. Instead, her dog Scout uncovers the mystery of a lifetime. A scratching sound in the attic leads to a loose floorboard. Beneath it: three ancient coins and smugglers' marks that haven't seen daylight in over two centuries. Together with her adventurous sister Jess and history-loving brother Noah, Alex discovers that their cottage hides something extraordinary-secret tunnels, hidden chambers, and a legendary treasure that vanished the night revenue men raided in 1784. The smuggler who hid it? Their own ancestor, Captain James Hartley. But they're running out of time. In three days, their family secret will be exposed. To solve a 241-year-old mystery, they'll need courage, teamwork, and one very clever dog. Some secrets are worth keeping. Others are meant to be found.