Incident on Ath (Dumarest of Terra #18)

Incident on Ath (Dumarest of Terra #18) by E. C. Tubb. mass_market edition. ISBN: 9780879973896.

An art collector seemed an unlikely prospect for information on the galactic coordinates of the forgotten planet Earth. But Earl Dumarest never overlooked any clue--and when he defended an art devotee named Sardia, he was unexpectedly rewarded by the sight of the painting she sought. For in its sky was the unmistakable features of cratered Luna, Earths equally fabled satellite. Sardia said the painter of the picture lived on a planet called Ath--and that was significant. So to Ath they went, she to find the painter, Dumarest to find the source of the accurate lunar presentation. But Ath was not yet Earth, and between the painter and the seekers stood the ominous forces of the Cyclan and the enigmatic insurrectionists called the Ohrm.