Along with other scattered survivors, astronaut Cynthia Han and the remainder of ISS Expedition 81 have finally learned what happened to the people they'd left behind, and it's worse than any of them could have imagined.

But even if life as Cynthia knew it is over, her struggles most certainly are not. Joshua Lamb, granted strange and inhuman abilities even as civilization died around him, directs his zealots to scoop up every pocket of survivors, to offer them the simplest choice: Join or die. The nightmarish Crooked Men still hunt the darkened, hollowed cityscapes. And towering over it all, the mind-breaking obelisks with their unreadable alien message.

At stake are not just the lives of Cynthia and her companions, but the last flickering embers of the human race. To succeed, not only must she learn the true purpose of the obelisks, she must come to understand that the worst of humanity's instincts and sins were never limited to us alone.