This novel's setting is a posthuman future, in which transhumanism long ago (during the mid 21st century) became the default philosophy embraced by the vast majority of human cultures.

Years later, the gleisner Karpal, using a gravitational-wave detector, determines that a binary neutron star system in the constellation of Lacerta has collapsed, releasing a huge burst of energy.

Stirred up by a paranoid Static diplomat, many fleshers suspect that Yatima and Inoshiro have come to trick or coerce them into "Introdus", or mass-migration into the polises, involving masses of virus-sized nanomachines that dismantle a human body and record the brain's information states as it is chemically converted into a crystalline computer.

Over the next few years, Yatima and other citizens and gleisners attempt to rescue any surviving fleshers from slow suffocation, starvation, or poisoning by offering to upload them into the polises.

The novel's title itself refers to a quest undertaken by most of the inhabitants of Carter-Zimmerman ("C-Z"), a polis devoted to physics and understanding the cosmos, along with volunteers from throughout the Coalition of Polises.

Though their physical infrastructure is not described, they apparently are hardware-based supercomputers of varying size (one of the full C-Z polis clones is briefly mentioned as roughly ten centimeters long) and unknown computational ability, all probably hidden in safe places.

By the beginning of the novel, the Coalition of Polises has existed for over 741 subjective millennia (during 910 years of flesher time), of which about 98.3% has occurred since the last major Coalition-wide polis hardware upgrade in UT 2750.

Almost all polis citizens, except for those who specifically elect otherwise, experience the world through two sensory modalities: Linear and Gestalt, which Egan describes as distant descendants of hearing and seeing, respectively.

Gestalt conveys information qualitatively, and data sent or received about anything arrives all at once for interpretation by the mind of the Citizen in all its aspects simultaneously, resulting in an experience of immediacy.

Early in the novel, for instance, Yatima learns about an asteroid in the real world by reading its tags subconsciously, which precisely inform ver about its properties such as mass, velocity, rotation, composition, emission spectra, and other such data discernible to the Coalition's satellite network.

Later on Earth, however, when ve and Inoshiro inhabit derelict Gleisner bodies, Yatima must remind verself that Fleshers are real people, even though they lack tags identifying themselves as such.