The Conjoiners have escaped upon their starship, named the Sandra Voi, to an ice planet called Diadem (which orbits the star Ross 248, 11.4 light years from Earth). It is home to an American colony, seeded decades ago by automated robots containing human DNA, but it appears deserted. Everyone is dead and seem to have shown signs of insanity before they died. Clavain is collecting the planet's native worms for studying. He and Galiana explore more of the colony, when they discover a corpse at the bottom of a crevasse. Upon closer inspection, they see the name on the man's spacesuit is "Setterholm". His helmet is detached from his suit, but Clavain realises that he would not have been able to leave the airlock without it being fully attached. He also notices the initials "IVF" carved into the ice nearby.
Later on, Clavain and Galiana find a man frozen in a makeshift reefersleep unit. The Conjoiners fit him with neural implants in order to revive him, and when he regains consciousness, he claims to be Iverson. He is unable to explain the initials that were carved by the dead man. He becomes good friends with Felka (who is now starting to become more human), but Clavain does not trust Iverson. He shows considerable interest in the worms, much like Setterholm was known to have done decades earlier. Eventually it occurs to Clavain that the letters "IVF" may have been the beginning of an attempt to spell "Iverson", with the man dying before he could finish carving the letter "E". However, he is unable to work out why the dead man would try to carve Iverson's name. In the meantime, he and Galiana are still unable to understand why everyone is dead, or why they all seemed to go insane. They eventually discover a sample of Earth bacteria that could have been altered to kill everyone. When they go to question Iverson, he and Felka are missing.
Clavain and Galiana chase Iverson to an ice cave, where they find him and Felka. Galiana takes Felka away, and Clavain and Iverson talk. Clavain has realised by now that "Iverson" is actually Setterholm, who killed the real Iverson and swapped the records of their identities. Setterholm had discovered that the worms and the tunnels they dug through the ice (which were coated in chemicals which determined which way the worms went down them, much like a human brain) had become a massive natural information processor, which he believed either was or was becoming a sentient mind. However, the American fusion reactor needed ice, the mining of which would have killed the worms. In order to protect this intelligence, Setterholm killed everyone in the base. Setterholm denies his identity, but Clavain proves it by smashing an ice pick into the worm colony, causing Setterholm to try and stop him. Clavain offers him the chance to leave, but Setterholm tries to kill him. Clavain then kills Setterholm by causing his neural implants to malfunction. He buries the corpse and returns to the others.