It is 5880ad., thirty five hundred years after both mortal and angelic civilizations destroyed each other in a war of meteorites over the immortality virus. In Alan’s universe the great houses of Centorin have founded the Empire and largely overcome the Aldeb threat. While this tale is happening, the Centorins have their own concerns in the mechanoid wars of the last years before the rise of the Overmarshall.
Meanwhile, a few hundred light years beyond the bounds of the Empire, a thirty seven hundred year old Angel seedship of Earth, fearing its cargo of eleven hundred frozen human zygotes may be the last of the human race, has been searching for worlds to colonize. They have done well so far, and seeded ten worlds toward the Perseus Arm. They are now down to the last few of the seed of mankind that they can sew among the stars and want to be sure these last few precious ones are given the best possible home.
Instead of a hospitable planet, they find a stone giant with too much gravity for human life and a microplanet that must be artificial. Then they find the microplanet using a communications protocol that could only come from the hack one of their crewmen did during their stay at their first study planet three and a half thousand years ago. That convinces their systems administrator that this must be a new hack, but she is unable to break it and must play along with the hacker's game.