[1] The initial part of the novel mixes near-future thriller and disaster novel scenarios, focussing on the discovery of a moving gamma-ray source headed towards Earth from the direction of Cygnus X-1, and the diversion of a Chinese-American Jupiter mission to investigate the new Solar System intruder.

Now imprisoned, the Sino-American crew attempt contact with the Cygnans and seek to discover their true purpose in appearing in the Solar System.

They discover the Cygnans have travelled for 6000 light years - and six million earth years - escaping a home planet orbiting the progenitor star of Cygnus X-1, having discovered it was on course to collapse (forming the black hole that now occupies that point in space), searching for a new home; and, to do so, have raided numerous star systems for Jupiter-mass "gas giant" planets to use as fuel.

With help from fluffy pink bird-like humanoids from 61 Cygni, fellow zoo exhibits from the Cygnans' last and relatively proximal port-of-call, some of the humans foil a last-ditch sabotage attempt and escape the starships just before the strange convoy leaves our Solar System.

Their escape requires securing a working example of the Cygnan annihilation drive, which humanity then develops into a much faster (though still, barely, subluminal) and more efficient stardrive, using the ice contained in comets to fuel their travels - instead of stealing entire planets.