TOYING WITH DANGER

Clark returns—with Sarah and his best friend Frog—for another ``Sarah Capshaw Mystery.'' When the three come across a Frankenstein robot in a barn, the discovery that it belongs to a toy inventor initially squashes Sarah's hopes for a monstrously good mystery. Then the friends find themselves in the middle of industrial espionage, with one toy manufacturer seeking information about the inventor's next creation in order to cash in on its potential. The kids' efforts run parallel to a private investigator's; this ``case'' probably would have been solved without Sarah's work and enthusiasm. Still, perhaps mystery fans are never too young to learn about the world of corporate dirty tricks, and the plotting, if without much panache, is sturdy. Periodic b&w drawings show the sleuths in action and root the high-stakes intrigue in a more homespun reality. (Fiction. (9-11)