The protomolecule has built a massive ring structure beyond the orbit of Uranus and humanity has sent a fleet to investigate. Holden and the Rocinante are there, and so is a church pastor, a security officer, and a Martian marine with unfinished business. When the ring activates and traps the fleet in an alien space, the danger is less the unknown technology than the humans trapped alongside it. Closes the first act of the series and opens the door to everything that follows.