Satan's World

Falkayn simultaneously discovers a lead on a potentially very valuable planet and evidence of a deep penetration of human society by agents of an unknown alien race, and must race to claim the planet for van Rijn and to head off whatever it is the aliens are up to. Right in the heart of the Commonwealth, on Luna, van Rijn takes independent action—breaking the law—to close down the alien spies, and then follows Falkayn to meet the aliens.