Swordmaster Ellus leads a small Butlerian cleanup force to destroy hidden cymek bases identified in records recovered from Juno’s database on Hessra. Although Omnius, the robots, and the cymeks have been defeated, Manford has ordered every remaining machine site eradicated before anyone such as Josef Venport can exploit its secrets.

As Ellus travels with six Butlerians and two other Swordmasters, Alon and Kelian, Ellus reflects on his Ginaz training and his bond with Anari Idaho. Ellus privately wishes for a worthy machine enemy and worries that, once all thinking-machine remnants are gone, the Butlerian movement may lose its purpose or invent new targets.

The team reaches a barren, airless world and discovers a damaged outpost covered with signs of a past battle between cymeks and combat robots. After docking, the group finds breathable air and functioning power, suggesting the cymeks once used the facility for experiments involving humans. Ellus refuses to study the surviving records, insisting that the place is inherently dangerous and must simply be destroyed.

The Butlerians spend hours smashing computers, samples, dissected brains, electrafluid reservoirs, and other forbidden materials. In the center of the complex, Ellus, Alon, and Kelian find a sealed, frost-covered vault containing a naked young man and woman preserved in cold. Believing them to be experiment victims, Ellus opens the chamber and revives them.

The twins identify themselves as Hyla and Andros. When the Swordmasters explain that the Butlerians are destroying the base and that the machines and cymeks have been wiped out, Andros becomes enraged. His flesh takes on a metallic quality, and he decapitates Alon; Hyla kills Kelian, breaks Ellus’s sword, and paralyzes Ellus by crushing his spine.

As Andros murders the remaining Butlerians elsewhere in the facility, Hyla reveals that she and Andros are the children of Agamemnon. Having been awake and waiting in the vault for decades, Hyla demands that the helpless Ellus tell her what has happened in the intervening years, then begins torturing him when Ellus refuses.