Hollywood has come to Half Moon Bay as kid inventors Nick and Tesla find themselves on the set of a big-budget superhero movie. But someone's sabotaging the on-screen debut of their favorite comic book hero, so the brother and sister sleuths must sneak behind the scenes to save the show. Luckily, they have help from an arsenal of homemade special-effects gadgets. This cinematic saga includes instructions for creating camera gear, stunt dummies, make-up...

Asked by a Bollywood star for help protecting a valuable ruby, Geronimo Stilton and Hercule Poirat are inadvertently cast in the actress's film in spite of limited acting skills and are horrified when an anonymous thief makes off with the ruby.