When Menrva, a geneticist in the subterranean city of survivors known as Bunker, responds to a call for help from Cowl, her former best friend, and Bas, a renegade cyborg, she makes a vital mistake and places all three of them in danger. As they struggle to escape City guards, cyborg soldiers, desperate scavengers, and ravenous aliens, they find in each other something they never expected: family.