Humanity has been decimated by a violent new species that nests in any enclosed spaces, and slaughters everything unfortunate enough to come indoors. Mitch is a 'Wall Banger', an explosives expert who 'cracks' buildings, exposing them to air and sunlight to kill these invasive organisms. When a friend of Mitch's asks for help tracking down a murderer, Mitch recruits Cori, a 'Shadow Runner' who races through infested spaces to gather supplies and saleable loot. But this terrifying contagion isn't the only danger, as their world descends into a harrowing marathon against oversupplied militias, murderous gangs, self-righteous survivors, and all-out starvation.