The evolution of Genestealers is divided into five generations—the first-generation hybrids look more like twisted, mutated, deformed monsters. Any sane person, except their parents, would regard them as unclean monstrosities. Second-generation hybrids look somewhat more normal, but still unlike humans. Starting with the third generation, however, things change. They gradually become more humanlike. As for fourth-generation Genestealers, aside from their slightly purplish skin, the plate-like protrusions on their foreheads, and their baldness, they are indistinguishable from the host species.
Fifth-generation Genestealers undergo atavism, reverting to pureblood Genestealers and beginning a new cycle of infection.
For the Inquisition, generally speaking, once traces of Genestealer infection are discovered somewhere, the safest course is to immediately issue an Extermination Order for the planet. Genestealer contamination of the host genome is irreversible, so completely eradicating them is the only option.
—The Inquisition's "Xenomorph Judgment Handbook," page 325 (with annotations by Grand Inquisitor Duanmu Huai: Anyone who sympathizes with Genestealers is considered a potential carrier and may be executed on the spot.)
Mary, who had thoroughly studied the Inquisition Handbook, had always harbored an uneasy question. That was—since the lower districts of this city were already teeming with third-generation and later Genestealers that were almost indistinguishable from humans, where had the first- and second-generation Genestealers gone?
Now, she finally had her answer.
The girls were currently staying in a residence on the outskirts of the city. Although the Governor had warmly invited them to spend the night at the magnificent Governor's Mansion, the girls naturally could not accept such an invitation. At Mary's insistence, the Governor had arranged a private estate on the city's outskirts as their temporary lodging.
Judging from the estate's lavish decorations, its original owner had probably belonged to the nobility. Clearly, however, he no longer lived there.
As for why, that