Enter Commander Keen - the alter-ego of an eight year-old genius by the name of William J. "Billy Blaze" Blazkowicz II, grandson of WWII Allied war hero B.J. Blazkowicz of Castle Wolfenstein fame.

When Billy learns that the Earth is in danger, he dons his brother's football helmet and his homemade interstellar spaceship to become Commander Keen - Defender of the Earth!

Keen Must Die! is the third episode of the Invasion of the Vorticons trilogy.

Upon saving the world from the Vorticon threat, Keen sets out for the Vorticon homeworld to find the Grand Intellect, a mysterious entity who sent the Vorticons to destroy Earth. Who is this Grand Intellect? Why does it want Earth destroyed? Do the Vorticons prefer wet or dry dog food? Stay tuned to find out!