As the British third-graders tell it to a BBC reporter at the Moulin Rouge, ""It all happened when we noticed a French car following us in Hampstead. With a bearded stranger in it. Only it wasn't really following us. It was following the taxi. And he wasn't really a bearded stranger. He was Inspector Thoreau! And the taxi wasn't really following us. It was following Miss Parker! Only she wasn't really Miss Parker, and she wasn't on the bus either. But I suppose that it really all started when Miss Barker bought a postcard of the Mona Lisa."" (Yes, there is a Miss Parker and a Miss Barker.) What happens between the children's class-trip departure from Hampstead and their honored reception at the Moulin Rouge is too deftly timed and meshed to summarize, and too funny to spoil. Let's just say that the action peaks with the theft of the Mona Lisa right before the third grade's eyes, and the culprits are apprehended when the ever-resourceful Morgan, bound and gagged with the other children in a chateau cellar, maneuvers himself into position to pop champagne corks and thus alert the old lodgekeeper to their plight. Brisk, bright, and bubbly.