The Great White Bum is using the brown hole to send prehistoric great white bumosaurs back through time to giant-brown-blobbify the human world into total bumblivion! With the help of Eleanor, his fellow bum hunter, Ned Smelly and Robobum - Ned's fully riveted, reinforced-steel, robotic Great White Bum - Zack and his behind must wipe out the Great White Bum forever . . . Bumageddon has begun.