Ferbin flees the Shellworld and seeks his sister Djan Seriy Anaplian, who left Sursamen years ago and became a CultureSpecial Circumstances agent. The gap between the world she came from and the one she now inhabits is the novel's central distance.
Chapter 1: Factory
The Shellworld's lower levels: Oramen, Ferbin's younger brother, navigates the political situation left by their father's death, unaware of what Ferbin witnessed. The medieval court politics of Sursamen are rendered with full seriousness.
Chapter 2: Palace
The palace and its politics. Tyl Loesp, the regent, consolidates his position. The novel's villain is shown doing exactly what successful villains do: making himself necessary.
Chapter 3: Folly
Ferbin's servant Holse accompanies him off the Shellworld and into the wider galaxy, providing the novel's comic grounding: a practical man confronting the impossible with the equanimity of someone who has always been at the bottom of hierarchies.
Chapter 4: In Transit
In transit: Ferbin and Holse travel toward the Culture, their journey rendered as a series of encounters with scales of civilisation neither of them has the framework to process.
Chapter 5: Platform
The platform where Djan Seriy is stationed. Her life in the Culture and her relationship to her origins are established before she learns what has brought her brother to find her.
Chapter 6: Scholastery
The scholastery beneath Sursamen's levels: the Oct, the Aultridia, and the ancient civilisations layered through the Shellworld's structure. The novel's deep history and its implications for the present crisis begin to emerge.
Chapter 7: Reception
The reception at the Morthanveld habitat, where Djan Seriy is redirected toward her mission. The Culture's relationship with civilisations more advanced than itself is shown as genuinely complicated.
Chapter 8: Tower
The Tower: Oramen investigates the thing at the centre of Sursamen that everyone has always known is there and no one has ever adequately explained. The Shellworld's secret is beginning to surface.
Chapter 9: One-finger Man
The one-finger man: a mysterious figure in Sursamen's lower levels who knows more about the Shellworld's true nature than he should. His presence is the first signal that what is underneath is waking up.
Part: Depth of Field
Depth of field: Ferbin and Holse finally reach Djan Seriy and Ferbin tells her what he saw. The family reunion is the novel's emotional pivot and the point at which its three strands begin to converge.
Chapter 10: A Certain Lack
A certain lack: the gap between what Oramen knows and what is actually happening around him. The political situation in Sursamen is deteriorating and the thing in the core is becoming harder to ignore.
Chapter 11: Bare, Night
Night, bare: Oramen at the edge of what he can understand, with the novel's central revelation about the Shellworld's purpose beginning to become visible to him.
Chapter 12: Cumuloform
Cumuloform: Djan Seriy's approach to Sursamen with Culture backup, the plan to address what is happening in the Shellworld's core, and the question of whether any of it will be fast enough.
Chapter 13: Don't Try This At Home
Chapter 14: Game
The game within the game: the full picture of what Tyl Loesp has been doing and for whom, and the larger forces that have been using the Sarl kingdom as cover for something considerably more significant.
Chapter 15: The Hundredth Idiot
The hundredth idiot: Holse's perspective on events as they accelerate beyond anything he was equipped to understand. His practicality and his dignity remain intact, which is the novel's quiet tribute to him.
Chapter 16: Seed Drill
The seed drill: what the Shellworld is actually for, revealed at the worst possible moment. The novel's science fiction premise and its human drama converge here.
Chapter 17: Departures
Departures: the movement of forces toward the Shellworld's core, the convergence of all three storylines, and the point at which the novel's scale expands to its full extent.