The Terra Data: Dumarest of Terra #22 (Unabridged‪)‬

That there was ever a planet called Earth, only Earl Dumarest believed. He had been seeking it a long time, though nobody else at the crowded galactic center believed in it. He had acquired some bits of information during his search outwards: a terrestrial zodiac, an authentic painting of Luna, a general series of hints that he was getting closer. Then he learned of a man who knew where Earth was, who had the special coordinates that would take a starship directly to it!

The man had lived on Elysius, and his widow knew where his data was. She demanded a price from Dumarest - a chore that involved a mining expedition, which would bring her back a fortune and him the information.

But Elysius was not the Elysium its name projected - and the terra data did not so rapidly come by!