Sally Tinker - creator of Brobot and the world's foremost inventor under the age of twelve - is back. Sally has built a machine capable of enlarging any object, but when she tries resizing a slice of pizza she accidentally enlarges a dung beetle to scary proportions. As the hungry beetle rolls itself a dung ball large enough to crush an entire town, Sally races to fix her new machine but not before Sally's baby brother Joe makes himself enormous and saves the day. Unfortunately Joe can't be shrunk down immediately, and he desperately needs a nappy change.