The protomolecule has constructed a massive ring structure beyond Uranus that opens a gate to thousands of other solar systems, and a flotilla of ships from Earth, Mars, and the Belt converge on it as a fanatical captain plans a catastrophic first strike that could doom humanity. Holden and his crew must navigate political intrigue, religious extremism, and the terrifying intelligence within the ring. The third Expanse novel shifts toward first contact and existential stakes.