Humanity has evolved over the years and in 2057 it has reached its peak in science and technology. Humans ships are hovering in outer space are taking care of different missions that have been assigned to them by the core. One of these ships is the awesome nuclear-powered ship known as Rockhopper. Under the leadership of Bella Lind the ship mine comets and it has been doing it for decades. Their current mission has been fulfilled and it is time to go home and get some rest.
Not another mission is expected by Bella so she too is in a mood to relax a little after a long troll in the space. Suddenly news comes from the central command and the ship is ordered to check one of the moons of Saturn. The moon known as Janus has started moving all of a sudden and it is going away from orbit. Another amazing thing is that it is not falling rather it is floating for perhaps flying in space like a spaceship.
There is a threat that it was never a moon rather an object sent by an alien race to analyze the whole picture before the invasion. Now if that flying object reaches its source or destination then the enemy that sent it in the first place will get all the information that is needed.
Alastair Reynolds presents a deadlier situation than Revenger and Revelation Space. Bella and her crew start towards the flying moon as quickly as possible and they now think that perhaps there are others like that which are hidden in the comets. If all of this is true then a huge alien attack is expected very soon from the outside world. Narration done by John Lee was up to the mark by all standards and there was no issue at any place.