The school year has ended but Lolo isn't exactly safe from Winkle's big ideas. She imagines their trip to London being filled with nothing but worry-free fun. Wrong Winkle finds out about a treasure hunt and talks Lolo and their cousin, Muff into taking part, believing he'll win the ten-thousand-dollar grand prize. Besides, what could go wrong? They're a part of someone else's game. But whose? Winkle disappears, and Lolo and Muff must decipher clues...