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!

The Earth Explodes is the second episode of the Invasion of the Vorticons trilogy.

After recovering the four pieces of his ship from the Vorticon forces on Mars, Keen returns to Earth only to find the Vorticons' own mothership hovering over the planet! Upon scanning the ship, he discovers that it has its deadly X-14 Tantalus Ray locked onto eight of Earth's most prominent landmarks - the Big Ben clock tower in London, the Egyptian pyramids, the Sydney Opera House, the Statue of Liberty in New York, the Eiffel Tower in Paris, the Roman Colosseum, St Basil's Cathedral in Moscow, and the White House in Washington D.C!

Keen must locate and deactivate each of the eight cannons, lest Earth's greatest landmarks be destroyed forever!