Greatfall: A Silo Story (Part 2) is the second installment of a dark new story set in the world of Wool, Hugh Howey's post-apocalyptic vision of humanity and its struggle to survive. (Warning: This description—and the story itself—contain spoilers from Hugh Howey's Wool Omnibus.) The dark nature of Silo 23 continues to reveal itself to Maya, who lies bleeding and starving in a cell on the uppermost floor, and to Isaac, the innocent boy selected to carry on the silo's terrible legacy.