Twelve-year-old Tessa was looking forward to baking cookies, relaxing, and spending time with her best friend Dennis in their Clubhouse, but with the sudden arrival of Katie - her perfect gymnast cousin from the US - Tessa's plans change. Katie isn't very nice at the best of times, but now has turned downright hostile, and is threatening to ruin everyone's summer. When they find a buried chest next to the local dolmen (their...