Two hundred years after humans first touched down on the surface of the Moon, there are permanent settlements there-as well as on Venus and Mars. The inhabitants of these colonies have formed their own political alliance: the Federation.

On the Moon, a government agent from Earth is hunting a suspected spy at a prominent observatory. He is caught up in the larger political struggle between Earths government and that of the Federation, and ultimately must struggle for his life-in the beautiful and barren landscape of the Moon under Earths light.