In a freak accident involving the Shrink Gun, a potted plant at the Docs' home scales up into a giant beanstalk taking Lamput with it! Up there beyond the clouds, the Docs and Lamput discover a giant world inhabited by a giant Mustache man. To make matters worse, Skinny gets trapped under the giant's shoe and is carried away to the giant's den. Specs and Lamput now need to rescue Skinny without alerting the giant and together they have to escape back to their world below.