Haine, the 'Stray Dog': a cipher of a young man with a mysterious metal collar bolted to his neck and a disturbing talent for mayhem. Badou: a hired gun for petty jobs both legal and illegal, whose reckless facade hides a serious intent. Naoto: a preternaturally skilled swordswoman searching for the assassin who cut down her family and mentor. Mihai: a middle-aged former hitman, trying live a quiet life but haunted by the deaths of his lover and protege. Driven by their ghosts - both dead and alive - and a desire for truth, all are inexorably drawn to the 'Underground', the dark and dangerous sector below the city that holds all the secrets - but secrets that can only be had for a price.