The Sentinel Force has protected the three remaining Marble Cities on the planet Centauris for centuries. They work to stop the Lontanus, a race of vicious creatures which are rapidly advancing and adapting their methods of attacking humanity. The people of the Marble Cities fear the increasing threat and thus the Sentinels search for a new member to add to their team. Will this addition be enough to keep the remnant of humanity safe on this brutal and unforgiving planet?