When the world's greatest masterpieces are stolen, it's up to three kids to track down the culprits! Henry, Anna, and Jose head from Boston to Paris for their most dangerous mission yet: to solve the mystery of an international art heist! Shortly after they arrive, they learn that a member of the Silver Jaguar Society is working as a double agent, passing information to the criminal gang the Serpentine Princes — but who could it be? When the senior members of the Society go missing, it's up to Henry, Anna, Jose, and their smug new comrade, Hem, to mount a rescue while staying hot on the trail of a missing masterpiece. Running around — and below — a foreign city filled with doppelgangers, decoys, and deceit, the three sleuths discover they're the only hope for the Society's survival!