When a smilodon is brought to Super Hero City from the Savage Land, a mysterious jungle lord named Ka-Zar shows up stating that the smilodon is actually his companion Zabu. When the Super Hero Squad encounter Ka-Zar, they learn of his mission and help him rescue Zabu. Meanwhile, Doctor Doom sees the Star Quartz (which will bind and merge any metal in the presence of Vibranium) around Zabu's neck and sends Toad, Thunderball, Sabretooth, and Batroc the Leaper to steal Zabu in a plot to reforge the Infinity Sword.

The Mayor's re-election bid goes awry when Egghead wins by a landslide (thanks to a little mass mind-control). But his reign at city hall makes life in Super Hero City a bureaucratic nightmare for heroes and villains alike. Wolverine and the Mayor are up against every hero and villain in a desperate attempt to free everyone from Egghead's control and stop the villains' planned invasion.