Heine Rammsteiner, a near-immortal gunman shaped by childhood genetic experiments, is one of four damaged people circling the same buried secret in a perpetually wintry, dystopian city. Badou Nails is a chain-smoking freelance informant; Naoto Fuyumine is a swordswoman hunting her parents' killer; and Mihai Mikhaylov is a retired assassin trying to live quietly. Their pasts all trace back to a hidden underground beneath the city and the organization that runs its experiments.