An asteroid containing a powerful ore known as Superium is being transported to Earth. The ship carrying it is attacked by Doc Terror. The Centurions save both the ship and the asteroid, but problems arise, when the Executioner, a master criminal who thinks he lives in the past, takes the place of Dr. Emerson on Earth. Emerson was to have given Crystal a special circuit to enable the safe beam-down of the asteroid to a secret location, but the Executioner instead substitutes it with a chip that takes control of Skyvault's computer. The asteroid is then guided to the Executioner's castle, ready for Doc Terror. With Jake trapped on board Skyvault, Ace and Max captured, the Centurions must find a way to stop both Skyvault's computer and the Executioner. Science Lesson: Asteroids by Ace.