The Long Winter is over. We survived. But only just. On a ruined world, we rebuild, watching the sky, waiting for any sign of their return. With only nine million survivors from a population of billions, humanity's survival is far from guaranteed but with the glaciers receding, there is now, at least, a chance. But out on the edges of the solar system, beyond Neptune's orbit, three vast asteroids have broken free from the Kuiper Belt and started the long fall towards the Sun. In two years time their trajectories will converge on Earth. We have to face the truth: they are back. And this battle will be to the very end. As humanity prepares its last stand in space and on the ground, it splinters. In our darkest hour, factions form and trust evaporates. And yet not all is lost. Dr James Sinclair has a plan that could ensure the species' survival, but it comes with enormous risks. Implementing it means navigating a course between two deadly enemies. One thing is certain: Sinclair's gambit will change the human race forever.