After preventing a nuclear crisis and revealing the plight of enslaved micedom to the human population, Amber, the valiant mouse wizard, and her partner Ben are ready for a rest. But Ever Shade, an ancient evil force has returned to Earth, and Belle Z. Bug, a giant mutant fly has hatched in a Los Angeles landfill.

In the twitch of a whisker, Belle Z. Bug's seductive multilevel marketing campaign enslaves a massive army of unsuspecting flies and throws the human race into chaos. When the mice's plane falls under attack, they join forces with the indomitable Harold Schortzenbeggar to confront their common enemy.

But their recent battle with evil worm lord Sebaceous Ooze saps heroes' vital powers. Will the victories won in Of Mice and Magic and The Wizard of Ooze come to naught as they face the sinister Lord of the Flies?