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 Earth's government and that of the Federation, and ultimately must struggle for his life--in the beautiful and barren landscape of the Moon under Earth's light.