Four Million Houseguests

A 3-D Imax film whose hook is microphotography: Anyone who ever wondered what a flea looks like on a 60-foot-high screen need wonder no longer. Elly (Charlotte Sullivan) and her parents spend the summer at the isolated country home of her beloved grandfather (the voice of James Garner), an amateur scientist who's on an expedition to Mongolia. He's left her a series of clues that lead to the "illuminator," a high-powered microscope that opens her eyes to a world invisible to the naked eye and filled with teeny-tiny -- but very scary -- spiders and bee-mites, jungles of bread mold and grains of salt like monumental diamonds. The only thing wrong with this film is to...