KAOS, tired of Hymie foiling their plots, has Dr. Ratton design Groppo, an indestructible killer robot. Groppo's sole purpose for being is to destroy Hymie, who is no match for his more advanced features. Dr. Harris upgrades Hymie, but he will need time to get used to his new abilities, so Max, 42, and Dr. Harris take Hymie to a ghost town for workouts. They then realize that the only way Hymie can defeat Groppo is to be reprogrammed for evil, but he refuses runs away. Max is then forced to fight Groppo alone. Hymie sees Max fighting for him and he returns, realizing that Max is his true friend.

This is one of the oddest episodes in that neither 99 or The Chief are in it. The part of 42 is clearly designed for the Chief, who missed several episodes in this time frame.